Mercule
Adventurer
We're talking about a hobby, here. The motivating factor in a hobby is to have some fun and relax. If 3.5 does this for him at an acceptable level, then it would be silly for him to commit to changing, at this point. He might take a look at it, later, and decide that it'd meet his needs even better, or he might not.
I don't think your friend is irrational at all.
On the other hand, there are people like me (and, from the sound of it, you) whose hobby needs are not satisfactorily met by 3.5. It would be irrational for us to stick with it. For myself, it's never been about 3.5 vs 4e. It's been Hero vs. Savage Worlds vs. 4e (or even nWoD).
It's all in taste and interest.
I don't think your friend is irrational at all.
On the other hand, there are people like me (and, from the sound of it, you) whose hobby needs are not satisfactorily met by 3.5. It would be irrational for us to stick with it. For myself, it's never been about 3.5 vs 4e. It's been Hero vs. Savage Worlds vs. 4e (or even nWoD).
It's all in taste and interest.