[Del Ozonator, I Thought Meant No Chemical Needed.]

Poollady hit the nail on the head, it does seem like 2-3 months is a bit extreme... did the Del company suggest this, or your dealer? My rule of thumb for hot tub draining is April and October. If you encounter problems before that, drain. If not, let it go as long as it's staying clear.

[Alternatives To Chlor/ Bromine]

I would recommend trying Soft Soak or Baqua. It's a little more maintenance, but I've never heard anyone coming away with a rash from it.