I just started riding after a whole winter off and I'm not in great shape now because of it.
So far I've done.... 10 miles and 16 miles. By mid season I can do 50 mile rides or more with no great problem, but it takes a month or two to work my way up to that comfortably.

If I feel a ride is too long for me for whatever reason, I just say so and I do a shorter one.