I may have to MR 1 or 2 nights to get to 20, but I don't see the value if you need many more than that. $2-3K can buy a lot of breakfasts or pay for some nice room upgrades.
Not a pure 20 night mattress run, as I'm moving a little bit of business and leisure before the end of the year back to Hyatt. But I may end up doing a few nights of runs to round it out. There's a reasonable number of Cat 1-2 near me, and I'm point rich at the moment, so P+C is in order. I'd been looking at getting the citi prestige card anyways too, and that would effectively take a ~25% discount off the effort.
Is it worth it? It really depends. This year I will hit Hyatt resorts 4 times with my family of 5, as well as 3-4 weekend getaways (mainly to regency properties). The suite upgrades + late checkout + breakfast easily provide 4 figures of value for me. But for a single traveler just looking for some free breakfast, probably not...