On your Snugride, are you having ANY issues with the center pull belt? I have re-threaded it twice. Each time it works better for a couple of days, then the metal threader thing seems to get stuck when I pull it to tighten. DH and I like Isaac in there very tight with the chest buckle pretty high up on him. I CAN get it tight, I just have to tip Isaac upside down, reach under to the metal buckle and pull it through so I can get some slack to tighten the center pull.
Does this sound normal? Probably not. I've just been dealing with it since he was about 5 months old, but like you, I love this seat and plan on using it until he's extended the length. Weightwise, he probably won't grow out of it until he's 4.