That's what's usually done.
I'm pushing 60 (just over 2 months away), but that makes me 50+ at least.
This AM I was doing my usual Thursday AM 25 miler before work. I'm cruising along at about 17 or so, which is typical, and a guy comes up behind me and passes. He's hitting between 19 and 20, so I hang on. I can do 20 for a while and even share the pulls.
After a mile or two, the guy picks it up. I'm thinking he either wants to drop me or he's trying to help me go a little faster. He gets up to the 23+ mph range, which is very fast for me, but I'm hanging in there, not in any real discomfort, feeling pretty good.
After a mile or so of that, the guy pulls out to the left and I move up and ask him if he wants me to pull for a while. His kind of snotty comment was "That's what's usually done". I told him he was a little fast for me, but I'd do my best for a while. So I pulled for about a mile at a little above 20 and then gave up and let him go.
I just thought the comment "That's what's usually done" was kind of dumb, but then again, I should probably have asked before I drafted on the guy. One of us was bit rude, either him intentionally or me unintentionally.
The good news is that I could stay with someone at that pace. It made me feel like a real bike rider!