There are circumstances where running the fan 24/7 can offset a problem like uneven conditioning of air in one room or perhaps a temporary band-aid for freeze up. Easier on the system? Not really,especialy the compressor which is the workhorse. Running continuesly will cost a little more for enegry consumed by the blower and quite a bit more for extra compressor run time. The continuesly circulating air will pick up heat from the ductwork in attic causing compressor to operate more. The rise in humidity is from air passing across wet coils. Useing pleated filters instead of fiberglass is how you get cleaner air.

I would not run blower 24/7 in AC mode at all. And when AC is not needed, only if you have a DC blower motor that uses substantially less power than a conventional PSC motor. I think your tech was blowing smoke.

IMO

+3. In a humid climate, unless you have significant air distribution problems, you don't want the fan running 24/7.