I let my STBXH know when to expect them, but he was served via Certified Mail, so that's a little different. If he was personally being served, I would've still let him know so I didn't run the risk of them not being able to find him.
My ex knew, and I had to have him served 3 times (at $125 a pop) because he'd dodge them. I finally sent them to his work and it pissed him the hell off.
It depends on your situation. I had to trick XH to get him served with the divorce papers. When he did get served he ripped them up and told the guy it "wasn't a legal serve". They guy laughed and told him that he was full of it. My ex dodged the process server for weeks when they were trying to serve him with the restraining order.
Re: STBXH getting papers soon...