experience from monsters stops increasing at floor 100, so most players just farm for experience around floor 100-110 if they are getting the Perks. you can go higher if you can, but you end up taking longer to get the experience, since monsters get tougher and the experience stays the same as floor 100.
another nice trick is fighting on floors divisible by 5, because at the end, you get the Elemental Boss for the previous 5 maps. killing them can finish one of the feats that drops a Legend item. when done, do what you said, and choose the same floor again and repeat.
so if you were on floor 25, cleared it, then fought the Slime Boss, and then chose floor 25 again, nice way for experience and extra loot.
on floors 21+, you can buy challenge maps of the same floor you are on. they give more loot that the regular maps, and they don’t have an exit, you either use the map of the Cartographer for the next floor, or go to the shop again and get another challenge map of the same floor. challenge maps are also more difficult, as they have affixes that boost monsters or lower some of your abilities, like lowering your ability to heal or get mana. they will have from 1-6 affixes, and the more affixes, the better the loot, but the bigger the challenge to get the loot.