@Tim Ivory,
The profit centers with a SLO are: non-refundable option fee, monthly cash flow, and backend profit when the tenant exercises his option. (I'm not sure what you mean by "renegotiating the final price." The price is set when you sign a lease and option agreement with your tenant. There usually is no "renegotiating."
Why are you concerned with, what you call, the "accrued equity?" Perhaps you are still confused about the process. Remember, you negotiate a purchase price with the seller. That is fixed. That's what you pay for the property when, and if, you exercise your option. You negotiate a price with your tenant that, in most cases, will be higher than the price you set with the seller. That is fixed. That's what your tenant will pay, when, or if, he exercises his option. The difference between the two is known as your "backend spread."
Once the lease and related option expires without being exercised the deal is done. Yes, you are out of the picture - unless you are granted an extension by the seller. And yes, that IS possible. But don't forget, the "seller" wants to get rid of his property. Why would he want to continue granting you extension after extension and continue to be a landlord?