Could it be that the insulation in the replaced Frigidaire was somehow degraded? They say that having a refrigerator that runs longer cycles is better for the motor - like in cars (where lots of stop and start on the engine increases wear due to the oil having to start moving around etc).
Our older freezer runs practically flat out in summer, and runs at around 0 cold, but in winter, I turn it down a little more, to keep it running.
The old freezer we had whose relay went POP! ran practically non-stop for around 8-9 years. I turned it down much warmer in the end, as it never got colder than around 4-5/10 (rusted really bad underneath).