I never understand these types of threads asking if someone should upgrade or if it's a waste. It's all a matter of personal priorities and personal comfort. Now that e500s don't convert into miles on expiration, the only waste is when these things go buh-bye after a year.

Why not go F? Does it matter? Personally, I can't sleep lying across rows. Personally, I'd hate to end up with a number of buy-ups and they sat them all near me. Personally, I upgrade whenever I can. Actually, I buy discounted F or C whenever I can and try to upgrade the rest. Doesn't matter... short or long. Of course, longer is better, but even on a relatively short flight, sitting in a nicer seat without rubbing shoulders with the person next to me is worth it almost every time.