Also not an expert in that field even if I am an electrician. As far as I know a heat pump is really just a way to say A/C unit that can also run in reverse. If everything is set up correctly it should probably just work and not need a service or "tune up" for a long time. It may just be that whoever installed the one you are using now wants to ensure that it's working correctly and as it should. Or... They may be trying to find something to upsell.