Is having an affiliated credit card (even if not used) generally a good way to avoid having rewards points expire? Also, any recomendations for good ways to use Amex MR points? I have to use the corporate card for business, but the points seem pretty useless (at my old company they let me use my personal SPG card)

I travel frequently for business, but- due to company travel restrictions- tend to have my points scattered among different hotel chains. I also have a decent amount of skymiles, but have found redeeming them for flights to be a complete hassle (and since I live in NY, and flying in and out is completely annoying, try to go on vacations to places within driving distance), so would like to use them for hotel stays. I'm considering getting an Amex DL card so I can use the DL points for Marriott and Hilton.

For context, my base card is an Amex SPG. I also have an Chase Amtrak card (no fee, good to have since I take Amtrak frequently), Chase Marriott, Chase Ultimate Rewards (which I'll probably cancel as soon I get the 40k bonus), a standard corporate Amex green card, and have just applied for an Amex Hilton I figured why not, since no fee and it's easy to hit the minimum spend for the bonus)