I'm trying to skip a segment without having the rest of my itinerary cancelled.

I'm have a multi-city ticket XXX-CLT-YYY and CLT-XXX. I'd prefer not to fly the CLT-YYY leg, since I'm trying to get to Charlotte-ish, and I booked this itinerary for price reasons. I know that if I skip CLT-YYY, then my return flight will be cancelled.

I'm flying the outbound portion this week. XXX-CLT or CLT-YYY may be delayed due to weather.

How far delayed does either flight need to be before US will let me cancel CLT-YYY (without cancelling the return flight CLT-XXX)? If XXX-CLT is so delayed that I miss CLT-YYY? If CLT-YYY is delayed by 1 minute? by 30 minutes?

When I was in a similar scenario a couple months ago: XXX-CLT was delayed by about 3 hours due to mechanical reasons, I missed CLT-YYY, and US automatically rebooked me on the next CLT-YYY flight. A gate agent and phone agent both warned that if I skipped the re-booked CLT-YYY flight that the rest of the itinerary would be cancelled. (I thought this was absurd: XXX-CLT was diverted for mechanical reasons, and that was quite enough adventure for the day.)