Depending on what kind of maintenance.
If you want to clean the blower wheel, which I'm now an expert after surveying 3/4 of Singapore, the jiuhu technicians expect you to do a "chemical overhaul".
You can forget about ALL the cheap servicing packages that do NOT include dismantling of the blower wheel. It's a half-fuck job that you can do better.
Chemical cleaning is not necessary, but dismantling of blower wheel is a MUST.
There is no need to top up gas. If you need to top up, that means somewhere in your system is leaking. You have to find the spot first.