> I can notice if something has not been worked on for a while, and act on it. Otherwise: out of sight, out of mind.

A visual indicator for task age works wonders for me. I use parentheses to show the age of a task. As the parentheses accumulate it's very obvious what I'm behind on. e.g. ")))))))))) respond to important email".

Works especially well for recurring tasks: the parentheses disappear when the task is marked complete.

I try to keep my lists as small and up-to-date as possible and this serves as a staleness indicator as well.

I use Todoist and have a script to manage the parentheses. https://github.com/leroux/todoscript

Credit to intend.do. I shamelessly stole the concept from NotDone Propagator. https://intend.do/features#notdones