The most important feature needed for tasks is not tables or recurring (tho that would be nice). What we REALLY need is the ability to print or export the task list. It is great that all the tasks from multiple notes feed into one task list, but working professionals quickly pile up hundreds of tasks, and they can't all be viewed or prioritized well in the current task view since the user has to scroll and scroll and scroll to see them all. We just need to be able to print them out -- or export them to a single doc where we can control size, group them by project, etc.
As for how long to access completed ones, your current system is great: showing them greyed out in perpetuity in the note where they were created but letting us opt out of viewing them on the task list.