The only technical limitation in terms of time you have for selling domain is the 60 day transfer lock.
Meaning that you cannot transfer a new hand-registration domain to another registrar for 60 days after you registered it.
The same 60 day lock is in place most of the time when the registrant name changes (change of name in the WhoIs information).
But that lock does not stop the ability to "push" the domain to a different account at the same registrar. So if you have a domain at Epik or GoDaddy, you could still sell the domain to someone if they also had an account at the same registrar (or they could easily create an account).
Beyond that it most certainly takes time to sell domains .. even good domain portfolios will sell anything between 1 to 5% of their inventory a year .. which actually means that even good domains take ON AVERAGE between 20 to 100 years to sell.
There are also some who say that depending on where the domain came from and who owned it before you, then there's a chance the previous owner tried hard to sell it before letting it expire .. but since it didn't sell then that means that at the moment most of the obvious potential buyers already said no. That is mostly not true as the vast majority of domains (particularly expired) were very likely not aggressively outbound.
Also .. there are people who try to predict future-trends and hand-reg (or acquire cheaply) domains that will be good for those future businesses. Like getting crypto related domains 15 years ago or Cannabis related domains 5 years ago, or drone related domains 10 years ago .. etc. For these domains waiting is simply because of the laws of supply and demand .. before the trend actually arrives there are no or fewer companies who would want the domain, therefore it is less valuable. But keep in mind that the majority of predicted potential future trends never come to be .. and the ones that do usually aren't exactly as predicted. For the most part (with some exceptions) I prefer to acquire domains that I has potential demand TODAY .. not 10 years from now.
In the end there is no reason to wait to sell a domain .. if you are buying domains .. it should be with the intent of selling them ASAP so you can then buy more domains and continue to grow. Sitting passively on your domains without even listing them for sale is effectively putting your money under your mattress and does you nothing but cost you renewal fees year after year.
You should obviously wait 60 days before listing your domain on certain marketplaces where a transfer is necessary .. but if you bought your domain at GoDaddy, then you can and should list it for sale at GoDaddy as soon as the domain hits your account (keeping in mind that even if it's a good domain it will take on average between 20 and 100 years to sell) .. after 60 days you should then list it everywhere else!