According to my observation, after the end of the sale, it takes at least one or two months, sometimes it takes more time, if you choose by quality, I think it may be longer, but as a result listing on a good exchange.
You are right, each project has a different roadmap including a schedule in the token listing. So we must understand the roadmap and always update information about the project from their official accounts.
Everything depends on the situation in the market - most projects don't enter the market because it'll lead to the fall in price! Nobody wants to hold alts, all want to fix their positions and wait!