would a guy normally last once engaged in sex. What's acceptable to providers (e.g. 20 minutes) without feeling awkward?

Every experience differs, I would have to comment YMMV. Sunny

When its up 4 four hours call the doctor.

Depends,1st timers have a lot of anticipation nervousness excitement,so once you get to it could be 5 min or less.Regulars pace themselves can go 10 min.

If you last 60 minutes or less than 1 minute, the bottom line is you have my time and attention. Try for as many rounds as you have in you. I personally never judge, I just want you to have a great time!

I don't have enough of an ego (I know...big surprise, right?) to care what I say here, so....
sometimes I amaze myself and can go for 45 minutes. Sometimes LittleDD just doesn't cooperate. Sometimes the cover goes on and he punches in his timecard...done for the day.

I spent too much time obsessing about this in the beginning. Treated it like I was with a civvie, mentally. Like performance was everything! Man, the stress.

Being fortunate enough to meet some of the most wonderful ladies in existence...everything is different now.
I approach it with the attitude of "We're going to have fun for a period of time". Maybe I'm a 'star' today...maybe not.
The ones who roll with the punches and have the same attitude...they're the best!

Remove any thoughts of time, lasting, or performance...and it's amazing what can happen!

Just sayin'

I agree with DD.  I do however tend to over analyze, which really wrecks a mood.

"When I was 20 yrs old I had no control, but now I have too much"

To be honest, if you're still pumping away after 45 minutes, I'm going to suggest we take a quick break because I'll have one crazy leg cramp

Yup, being over 50 is not for sissys. Thank goodness for Viagra. A buddy of mine once said "I've screwed so many times at half mast that now I can push my lawnmower with a wet rope".