This is quick & easy. When you’re making a Powerpole connector, shrink a length of small heatshrink tubing over the end of the terminal after crimping.
You can’t cover the entire crimped region, lest the terminal not snap into the housing, but halfway seems to work fine.
The goal is to keep the wires from flexing right at the end of the terminal, which is exactly where they’ll break.
I’ve also wrapped a length of self-vulcanizing rubber tape around the entire connector housing and the wire, which is appropriate for high-stress applications. Looks hideous, though, not that that matters much.