I've been saving Total Rewards points and MGM Express Comps as retirement strategy, though I use a few now and then. Same with the Southwest Airline points.
On the flip side, food and other things we use those points for will generally rise in cost, so it may be foolish not to go ahead and use them now.
Plus, with CET, you lose them if you don't gamble at a CET (or use their credit card, etc.) in six months. MGM gives you 18 months, I think. Anyway, God forbid something bad would happen and I couldn't keep the points current, so another reason to use rather than risk losing them.
A zillion years ago I forfeited about $350 in cash (way back when you could cash your points in for money) when one of the first riverboat casinos in Tunica sailed away to another location (blanking on the name right now). We heard it was leaving soon, and drove the 3 hours to collect my points, only to actually witness the boat pulling away from the shore. Damn!