I just made a reservation on 2/2 from LAS to PIT. I already received a reservation changing the flights in both directions. Going, it change the first flight to 2 hours earlier which sucks but OK. However, returning from PIT, CO considers 35 minutes an appropriate connection time in IAH. I find that too close for my comfort, especially on at 5:00 on a Monday evening. I don't have status. Is there a way to require they change the flight? What is the number of hours the flight must change before CO/UA must accept changes without charge?
I'm on hold with Reservations. Wait time is approx 30 to 35 minutes.

Thanks for your information and advice.