The dealer garages do push these cleans/flushes a bit too much in my opinion. Obviously the more miles you do, the more dust, dirt and probably bacteria accumulates in the air passages and evaporator. Checking the condenser for fouling isn't something I have done. Aircon inspection is shown under "Recommendations" on the health checklist, but the service checklist doesn't have a line item for it.
Our car is 4+ years old and has done around 38K miles and probably does need an aircon clean. It's working ok, so don't fix it. However, I think I'll probably buy a can of cleaner and do it myself, but not until next Spring.