Agreed, but it is also easy to see the tension in your second paragraph. You can plan to rewrite everything at least once, but you will never get that actually

Agreed, but it is also easy to see the tension in your second paragraph. You can plan to rewrite everything at least once, but you will never get that actually in the plan. My only somewhat clear path out of it is to make sure you built it so it will be easy to rewrite. Either do the least that you can, or keep an eye for improvements, but don't necessarily act on them.