My commute is exactly 10 miles each way and I do it once/twice a week. I don't think I'd want to go much further, although if it were any longer I'd switch to a road bike. I'm a fair weather rider too, I don't ride in the rain/snow unless I get caught. Even today, no rain but 95 degrees and I didn't ride. I may hop on a Citibike though on the way home, which is a nice option.

I'm just picturing in my head where 25 miles gets me, and how I'd feel when I got there, and no thanks. That's just too far. I leave the 50+ mile rides to the weekends.