I'm in a 10 year old house where the original owner lived year round. I use it only in the summer and turn off the heat while I'm not there in the winter. The ceiling joints were fine when I bought the house 2 years ago but after the first winter with no heat several ceiling joints started to peel with the gyproc tape now coming off or bubbled.
I assume the cause is no heat in the winter and I'm looking for a permanent solution which allows me to turn off the heat each winter.

Why is it only in the ceiling and is turning off the heat the real cause?

You are probably getting 100% humidity in the house with the heat off in the winter. Might even be getting a lot of condensation in the attic and the joints are open on the attic. Water trickles down and you get peeling. Need to keep some heat on, even if it is set at 50.