With new blades, washed, dry, clean horses with a normal fur length mine last for about 3-4 horses. With only previously clipped horses probably one extra, so 4-5. With dirtier, fluffy or rough furred ones its probably one less. I always clean them right after using, and sture them damp free and clean wrapped in toilet paper. Oiling your machine also helps durability a lot too.
I think you’ll be fine, just keep an eye that they’re not pulling the hair.
You can get the blades sharpened. If you don’t have a local tack store to drop them off at, ask a hair salon where they get theirs done.