Newb question, how long.

Due to my always smoking before going to sleep, I often left bowls sitting overnight to be finished the next morning. I found no significant deterioration of flavour. However, I would not leave the bowl uncleaned for too long as your pipe will need to breathe rather sooner than later in order to dry out, particularly if you have a small rotation. A sour pipe tastes awful and is difficult to remedy.

Some tobaccos change character and even get better if you use DGT... Delayed Gratification Technique.

Experimentation is key. (That's my superior sounding way of saying "I don't know.")

Just the other day I was working from home, I set down my pipe to take a phone call, walked inside the house and was on the phone for 45 min, then ate lunch. Came back to my pipe about an hour after setting it down and it was fine. No problems.