There is a lot of answers to this question. Haha. I did a cross country season with 1 set of tires and sealant. (Stans sealant)
As I’m sure you may have noticed, the sealant will seep and sweat depending on climate. It all depends on the brand of sealant used and weather you ride in and how often you ride. Here is a good article to skim through that explains it pretty good. A lot of popular bike brands say 6 months
hope it helps!