While I *might* consider moving outside of the AirBnB platform if a guest said they wanted to become a standard "renter/tenant" for at least a year, I otherwise recommend staying inside the platform for all short-term guests. For one thing, making deals on the side violates the agreement you have with AirBnB. Do you really want to be that kind of person? For another, AirBnB's various protections (security deposits, insurance, mediation) won't apply if you make side deals. I firmly believe that the kind of guest who asks this sort of thing is the kind of guest that will eventually burn you.
And when I said I'd consider a year-long tenancy outside AirBnB (at an appropriately high rate), that would only be because I would suspend my AirBnB listing and go back to a normal owner/tenant lease as I had for years before switching to AirBnB.
As long as we're using AirBnB, we'll operate inside their rules.