This week I went on UA 1035 from IAH to UIO and can right back on UA 1036 to IAH , I had the same plane crew we just had 70 minutes between flights.
It's 5 hours down and 5 hours return is a lot of time for a crew to be in 737 , also the flight leaves at 5 pm and comes back at 5 am.
Not even CM does that with all their flights to South America that are 5 hours they change crews