A lease option is usually a combination of a lease and an option-to-purchase, both of which run for a specific length of time. I like Andy Heller and Scott Frank's material on this topic. In their approach, they agree with the tenant buyer on a purchase price up front. If the tenant buyer chooses to exercise the option, they will get their own financing and pay you off. If they choose not to, but don't want to move out at the end of the option period, you renegotiate and extend the lease and option or write new ones.
So, yes, it could go for a long time. But, it could also get terminated for any of the reasons a lease usually gets terminated. Not paying rent, illegal activity, whatever. You would write the option to refer to the lease and state that if the lease was terminated for any reason that the option was also terminated with no refund of any option payments. In theory, that gives them an incentive to keep up on the rent and take care of the property. In reality, who knows.
Heller & Frank's course has forms with it.
Thanks for that compliment.