Maybe I'm the odd one out, here, but my husband doesn't HAVE a guys night out. He has no interest in going out to bars and hanging out, etc. He works a rotating shift, so when he is home in the evenings, he wants to be home, with the kids.. not something he always is able to do.
He does, however, have a "golf day" where he goes on one of his days off and spends the day golfing with guy friend(s). We just added the "average" amount to the monthly budget items, and it is a non-issue. I know that every Monday, he is going golfing, and will be up and gone usually by 8:00 a.m. and not be back home until around 3:30 in the afternoon, depending on where they go to play that day.
Usually, he is home in plenty of time to relax a little, grab a shower, and then help with the kids/dinner/homework, etc and have a nice evening at home. On special occasions (around his birthday, or his friend's birthday) they will sometimes drive to a better course a little farther away and end up being gone til dinner... but he always lets me know when they are planning something like that. And he calls me when they leave the course so I know when to anticipate him getting home.
He NEVER plans things that will interfere with his ability to sleep adequately to perform his job. And if the kids have anything special going on (a school event or sports or whatever) he will make that a priority, and he will either be back in time, or skip the golf.
Family comes first, but he also needs that "guy/golf" time to decompress so that he is ready to devote his other time to us. I have learned that mentally "deciding" that he has a day "to play" is good for US as a couple and US as a family, NOT just for my husband. It helps him be a better husband/father.
(oops, guess I should have read the other responses first, I see they don't really "do" guys night out either, lol).