For me, commuting biggest variable is always the roads you ride on. Around here, some of the roads are perfect for bike commuting and others are suicide. I will say for the most part it is easy to get around down here on a bike. But I will only ride to clients that are within 15 miles and if I know I have a place to change real quick. If the roads are unsafe, I would not even consider it.

Commuting more than 30 miles each way is ludicrous in my opinion only because you are stopping for such a large period of time and then restarting. Your muscles have too much time to get cold and not enough time to rebuild. This could make the ride home ridiculous for anybody despite their shape.

Having the right safety equipment and storage helps plenty as well. I tend to use my pannier bag/s if it is real hot or they are farther away than 5 miles. Inside of 5 and on cooler days I don't mind just throwing on the Laptop/Backpack Case and riding the short few miles with it on my back. The lighting is very important as, you tend find yourself get caught off guard with leaving work on time a fair amount. Riding home in the dark without lights is NO GOOD.

I am a youngster at almost 30, but plenty of guys I ride with and that commute around here are well into their 50's, 60's and even 2 guys that I know are in their 70's. They both ride over 10 miles each way for their commute.