They have variable speed blower motors &/or Condenser Fan motors, Shuffler...
save, your HVAC system should not be leaking any refrigerant at all, regardless if it is R-12, R-22, R-134A, R-410A, etc.....
I installed the Trane Heat pump system in my parent's house in May 15th, 1994 and it has never had any refrigerant added to it to this day..only needing changed out the contacter twice and a combo-capacitor once...at the time of installation I installed a "whole-house" surge protector along with separate surge protectors each on the Air Handler and Heat Pump Condenser...as well as a whole house Side-mounted Duct Humidifier, (2) Bioclimatic Ionization Air purifiers, Commercial grade electronic Air Filter backed up by a Spacegard model 2200 6" thick pleated filter...a 7 day /4 times a day programmable thermostat.....
With that being said/done... A heat pump is not and was not ever designed to "HEAT" a home, dwelling or business... Heat pumps were designed to "MAINTAIN" the heat in a home, dwelling or business...
As for whether to leave a heat pump thermostat at a constant setting verses lowering it while one is away from home then raise it once they have returned home... One would do better to leave their thermostat at a constant setting...
As to closing off supply & return vents to a room or section of the dwelling would only cause one undue energy consumption, because this allows the cold to overcome the perimeter and allows the cooler air to reach further interior walls/doors...this applies to both the heating and cooling seasons
As for water-heaters that can also heat homes...these systems have been around for over 30+ years, and have only gotten better with efficiency...as have water source & geothermal heat pumps
As for those that use gas furnaces (natural or propane) are ideally suited for programmable thermostats, same goes for oil furnaces (and for those that have Electric Heatstrip furnaces)
Back to those that have to add refrigerant to their AC or Heat pump Condensers... Regardless if you are talking about a freezer, refrigerator, vehicle A/Cs, residential/commercial/industrial cooling systems using any type of refrigerants...all these different type of systems are what are considered as "closed-loop" systems designed to never needing refrigerant refilling, topping off, etc... Once installed and initially started up and refrigerant charge checked accordingly....if jt is found to be low on refrigerant, then a HVAC&R Service Tech is allowed to top off the system if it is less/lower than the allotted amount allowed by law/code and should be scheduled for a follow-up service check to see if it has leaked down any given amount...if it has a leak check must be done and solutions on what to do at this time should be discussed...
I'll stop for now and read up on replies
Hope this was of some hel8
TC