First you have to regularly get those, with my usual RNG I hit one upgrade ever 3-4 rounds, so that's generally a less than viable 'meta' for my runs
You should get an upgrade every 2-3 rounds which results in plenty of upgrades over the course of the game.
Unless they show up with a heal while you need it, which, with my RNG, is usually when they show up
Normally, in my runs, I don't need the heals so idk.
