It seems crazy, but I get a lot of users asking me how to turn off alerts for to-dos that they completed months ago. They've been suffering in silence for months! haha
What isn't obvious to the uninitiated is that a to-do is a checklist item that must be "checked" to be completed. Solution could be as simple as some additional messaging about what to do when you've completed your to do.
Thank you for the idea. Given the low volume of support for this idea, we do not have plans to make updates in this area at this time.