I've discussed working hours previously. My maximum daily number to retain sanity is 13 (barely), but the number can go up from there if there's an emergency or if it's a travel day.
When I get back from a long day in the field, say, more than 12 hours, all I want to do is eat, decompress a little, and sleep. On occasion, though, I've worked with someone who is just ending either a 60+ hour work week or a 14+ hour single day, and starts coordinating a full night out with friends. I've listened to plans for clubbing or other high-energy hijinks with amazement. How on earth do they do that?
I mentioned this to a coworker, who noted that the folks going partying tended to be in their early-mid 20s and hadn't hit the post-30 metabolism/energy drop. Post-30? Hell, I've been doing this since immediately after graduating college, and at no point did I ever have the energy to do more than make dinner after a long field day.
I may be a wee bit of an outlier, though, for 3 reasons:
1. I'm an introvert. So spending an evening being social on top of a long day in the field would destroy me. Or at least make me a big party pooper.
2. When I was younger, I was often thrust into situations that were high-stress just because I wasn't experienced with overseeing surly drillers or dealing with the inevitable field snafu. I've gotten infinitely more comfortable with fieldwork and I'm much better at stress management, but I am probably feeling the effects of age more.
3. I'm a naturally high-energy person, but not an infinite-energy* person. When I'm in the field, I'm constantly moving, either popping up to adjust something, pacing during a phone call, or scurrying to collect something else I've forgotten. I do fine until I get home and sit on the couch/flop into bed and release all the tension I've been carrying, and then I'll need to be peeled off whatever I've landed on in order to shower and eat.
So when you were in or just out of college, did you go out and do active stuff after a long day of fieldwork? And if so, were you able to keep up that pace as you aged?
*I do have a friend whose bipolar disorder manifests almost entirely on the manic side. With medication, fieldwork, and a serious slate of physical hobbies, he doesn't need to be pried off the ceiling quite as often. He is very much an exception to a discussion of energy levels.