One thing I’ve learned with the larger-scope projects is that you need to estimate in time for providing assistance using them to the client. I always included training time in the estimates and for larger projects that was decent, but I’ve done several projects lately where clients have specifically requested the ability to change or re-use portions.

What I never considered is the level of support they’d need when attempting to re-use the product. Even though it’s ten minutes here and there, that time builds up, so you need to be able to estimate that out.

If you find it difficult to estimate, then perhaps it would be better for you to offer a monthly recurring fee similar to a retainer. This allows you time to provide support, brain storm about changes or improvements, etc.