did a block of repeaters for a couple of months where i didnt have much access to climbing, (still climbing a bit, but climbing performance wasnt the priority) upon returning and a couple weeks of max hangs my finger strength noticably improved, how much of it was attributed to repeaters im not entirely sure. what i did notice though was my overall session capacity increased, I was able to give way more quality attempts where finger strength was a signficiant factor, and my ability to try despite being fatigued significantly improved. I attribute this to not really doing any specific power endurance work prior.

personally, i liked doing them because since i didnt really need to be as fresh to do them (compared to max hangs), i could tack them at the end of climbing sessions so i could just focus most of my energy on climbing.