Considering that a lot of questions got good answers just a few minutes after the question, and that some people need more information for better understanding and better answers: how much time is polite to be 'outside' of Stack Overflow once a question was posted and then return back to check answers and comments in your question?
Difficult to tell. Very often, when people ask questions, they will return after a few hours to check on the progress.
It also depends on how badly you need an answer, I guess. A comment that doesn't get answered quickly will simply be forgotten by users, until you respond.
You get the Fastest Gun In The West answers for at minimum the first 5 minutes after you post. Usually a crappy version, quickly typed to get lazy upvotes or to lock-in the Enlightened badge. Meanwhile, the answerer still works on typing a real answer. Give them another 5 minutes in case they were a bit late to seeing it. Posting a comment that says "what do you mean" is a waste of your time, wait 10 minutes.
Find a sword to pass the time.
When fifteen minutes have passed and you still didn't get a meaningful answer then you've got a problem with your question, it isn't good enough. Jump in and start editing your post, you'll need to give a lot more details. You have however entered the very long tail of SO, your edit can only bump it up-hill a bit. The odds of a sugar daddy showing up to cast the spell are low. Start looking around for somebody else's question to answer so you have enough rep to put a sizable bounty on yours.