Mikes got it right there. Whenever I am looking to deal with someone on some pricey items (buying or selling), I’ll check up on them and appreciate it if people do the same with me.
If someone gives me an offer on something, I’ll give them a timeline, usually a week or so if it’s an item of lesser value. If the person doesn’t keep up the communication, I feel no obligation to hold it for them. I will, however, keep them informed of whats going on. You don’t want to be a flakey seller either.