Say you have a money back guarantee period (30 days seems reasonable), and if they push and you feel it's worth it still, offer to extend the money back guarantee period. If someone wants a thing but absolutely will not pay for it, that's typically resolved by them not getting it.
I'm not aware of any good reasons, but I think GAAP standards say you can't recognize the revenue until the returns period ends? I think standard wisdom is to not have an official policy so as to keep the books simple (and maybe to avoid the downside I can't think of for returns periods) but use refunds pretty aggressively in support?
Your company should be on cash-basis accounting. Unless you have a need for accrual based. When you file corporate taxes, you list the method of accounting you are using.