My AC unit compressor is needing to be replaced for the second time in 10 years. Is there something wrong with the main system?

There could be a problem. Some of the causes can be that the unit is too small for the job and its getting overworked. Is wiring to it in good shape? Getting adequate power?

Another thing is many compressors do come with "lifetime" warranty. So be sure to check your paperwork before starting any repairs.

If the unit wasn`t flushed out/cleaned correctly /cleaned with a good acid remover,it is very likely that the newer compressor would go bad,, the cleaning includes the copper lineset,the evap coil ,and the condenser coil