The time horizon for my to-do list is a week. Further out than a week is probably a scheduled item which is a different thing than a to-do.
Everything else is an idea among my notes. My backlog is my notes. It's the place where I go to jot something down and then forget about it until something happens to surface that item again. If that happens, then maybe I'll act on it. Maybe I'll just add to the note and forget about it again.
Anything on my to-do list which isn't done a week from being added gets turned into a note, to be forgotten about.
Information dense project task flows aren't to-do items and I manage them in a proper PM app rather than a to-do app.
I think it's important to be constrained with how you use todos. My list is short and easy to manage. Even being memory and attention challenged, it's easy to get a quick grasp on everything I need to do for the next few days.