I'm not familiar with Wynn's system nor do I have personal experience with slot comps since I don't play slots, but I'm pretty sure most casino families, including MGM and Harrah's, accumulate points for slot players. They may expire based on certain stated periods of inactivity, but otherwise can be combined for future stays.

Table game comps are of course a different story given the subjectiveness implicit in systems in which casino hosts decide comps.