Multis that lasted a long time for me (over 12 hours before I started playing more aggressively) are RIP Control, Prince Premier Attack, Discho Microfibre, and Kirschbaum Touch Multifiber (all 16 gauge).
My problem, lately, has been that I've started playing more aggressively from the baseline, and now I'm breaking multis in under 5 hours, usually with a shank. PPA and KTM have both been prone to premature breakage on shanks. I haven't tried DM lately because I try to fill my TW orders to get free shipping, and they don't sell it at TW.
I might try a setup with RIP Control in the mains and PPA in the crosses. RIP Control 16 is probably the most durable of the bunch, and I'd like to see how it stands up to shanks. I prefer the other strings on the list for playability.
I'm also playing with natural gut on one racquet. Gut definitely takes sudden stress better than synthetic multis, but it's expensive and doesn't hold up well in when it gets wet, so I always bring a spare racquet with multi.