How much HP washing is helpful for a hero?

I mean generally, how much HP washing done to a hero would help it with bossing, survival, etc? (in terms of # of washes) Hopefully not much since funding a godly 1h red katana hero would be a pain. >_>

I plan on making a hero in the near future. I don't play on selling my mage's gear so I have INT gear for HP washing.