> didn’t systematically leave redundant pull strings

I don’t leave redundant pull strings and rarely even pre-pull the first one. Only if the conduit is going underground do I pre-pull (before it takes on water).

Install the first with a shop vac and a “mouse” made of thin shopping bag.

When I use a pull string, I pull a replacement one in. In a conduit I expect to get repeated changes, I might install one twice as long plus about 12 feet (4 meters) and tie it off at both ends.