> If you make a good product, customers will come back to use it again and again. They won't just forget about a product that worked wonders for them.

Ehhh I can turn that around. If you make a good product, customers will have enough confidence in that product to not want to consciously have to make a payment on a recurring basis. I'd suggest it's not something necessary for your product to succeed, but it's something your customers will probably want.