We have a 3 bedroom house. Originally we had master br, guest room and office. When DS was born, one of the rooms became a nursery and we combined the guest room and office. In the process, we put a lot of stuff in boxes and shoved it in our crawl space. For a while we had our house on the market and at that time we got a storage unit so that we could declutter. So now we have a bunch of stuff in a crawl space and in a storage unit that we keep saying will come back out when we have a bigger house. And we're having to box more stuff up as our guest room/office becomes another baby room. At this point, I'm thinking we should just get rid of absolutely everything we don't have room for and definitely stop paying $50/month on storage. A lot of what we have boxed is books. We went from 3 bookshelves to 1 and now we'll go to zero (we bought kindles). It makes me sad to get rid of books, but really, is it smart to hold on to all of them? We also have a lot of decorative stuff and even some kitchen stuff, but our kitchen is bursting at the seams. Some stuff is obvious that we should keep (like the camping stuff that is only used occasionally, but is used), but other stuff is a harder call.
So, what's your general rule of thumb? Do you keep everything that you might use someday, or do you purge everything that you're not using right now? Or somewhere in between?

Re: Keep vs. purge
I follow the 6 month rule: if I haven't used it in 6 months, I probably don't need it and it gets donated to the Vietnam vets. This doesn't apply to my grandmother's Noritake china and my aunt's sewing machine, obviously, but clothes go out of fashion/wear out and books don't serve much of a purpose after you're read them (with a few exceptions).
Have you been visiting the storage unit to pull things out? If not, it might be time to go through it and see what needs to go. Honestly, I have very limited patience and I would probably just cart the whole lot of it to charity and let them pick through it, as long as I knew for sure no important files were in there.
My rule is it goes if I haven't used it in a year, it goes (that way all seasons are covered). I try really hard not to keep things "just in case". There are some obvious exceptions (family heirlooms, things with sentimental value, etc.).
I am funny about books though. I do not get rid of books. Ever.
There are a few specific items we have gone and pulled out of storage. The last was the baby name book
But, for the most part, it just sits there
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I am the mindset of when in doubt, just purge. When it comes to books I only keep my favorites that I know I will read again and enjoy just as much, the rest go to Goodwill or friends, I don't expect to get books back from friends, I expect them to keep sharing with others. Which I am happy with because I buy a lot of books from Goodwill (I would never buy a book from Barnes and Noble, they are just too high.
I think if its hard for someone to let go of things then the one year rule is a good one to live by. Family heirlooms are an exception, but you still have to limit it, I have a cedar chest passed to me by a great aunt, and all of my family heirlooms fit in that, period. The only exception is an heirloom set of china that is on display in a cabinet in our dining room.
My feeling is that if you don't have it on display or you aren't using it frequently then you really don't love it. But that is just what works for me, good luck.
Baby Girl Lennon born sleeping 6-18-11 Baby Boy Anderson born healthy and happy 8-17-12
Our rule is that we will never have a storage unit. My mom had one and it was a pain to dig through to find something. We purge stuff at least once a year. Last September we sold $600 worth of stuff on Craigslist. I am thinking about doing a garage sale at the end of June (we want to find out the sex of the LO first to see if we need to sell all our girl stuff). I don't like clutter and I figure that most stuff can be replaced if I ever need it later on down the road.
my read shelf:
I'm going through the same process right now! I just took a cleaning break to hop online for a bit.
I'm more of a keeper than a purger, I have to say. But I do have my limits -- DH and I swore we'd never wind up with so much stuff that we would need to pay for a storage unit. But I have to admit I held on to a bunch of my old toys, stuffed animals, children's books and things "just in case" I ever had a kid one day. Yep, I carted that stuff from apartment to apartment in my 20s. I'm glad I have it now, but I'm still not sure if it was worth boxing up and storing all of those years.
With kitchen stuff and non-sentimental decorative stuff, I say purge. It's nice to think that you'll move to a larger place and need those decorative things again, but people's tastes change, your color scheme might change, and you might wind up keeping it only to get rid of it when you eventually move.
(says the girl who still has all of her old framed posters from high school and college... oops...)
I love books desperately, but, honestly, it feels good to give them away! Especially if they're old paperbacks, or classics. You can get a lot of the classics for free on Kindle now, and paperbacks just don't hold up that well over the years. I hold on to hardcovers and newer paperbacks, but older ones I will pass on to friends or to my mom and let them keep them.
My biggest problem, cleaning-wise, is the amount of sentimental stuff I have. I kept diaries and journals religiously as a kid, and wrote tons of stories (still do, but it's all on my laptop now). So I'm faced with dozens -- literally -- of journals and notebooks that I don't want to get rid of, but that take up valuable real estate in our verrrry small house.
With the exception of books, if I haven't used something in a year, I donate or toss it.
I'm weird about books. I keep them all. I still have all the books I read as I was growing up.
Me too. They have sentimental value to me.
I'm a binge purger and DH is a hoarder, so we have issues.
I got rid of a crapton of stuff last summer/early fall by going through the basement but the problem is, DH is in publishing so he gets packages daily and the basement is getting full again. We need to go through the basement again, this time with more of DH's help and just get rid of the junk down there.
With this new baby, we're going to lose our guest bedroom and need to make one in the basement, along with DH's office. Its not going to be fun.