For example, I had the hvac guy come to do the annual check on the furnace and the tenant managed to talk the repair person into changing out the thermostat even though it was functioning, she just didn't like it. 

One fix to control heating / cooling costs I've implemented is lockbox around the only thermostat in the property (not ideal). 

I have lowered the thermostat to 70 degrees and it is running all the time.

@Nitanth VangalaLook into AC Optimization program thru LADWP, you get a free Nest thermostat

All that being said, I have seen situations where tenants complained about ovens not cooking properly and it turned out to be a bad thermostat.

Treat it like you would your own house if managing yourself yearly inspection :- furnace/boiler - clean out burners (do in Fall to make sure heat is on in winter)- clean dryer vents- caulk bathtubs- change out thermostat/CO2 detector batteries- clean out gutters in Fall- while on the roof looking at gutters, take a look at roof condition - fix early- vacuum and clean utility room near any furnaces and water heaters (keeps dirt/dust out of systems, can extend life)- rinse water heater screens (can fill with dust and won't stay lit)- drain water heaters yearly - prevents sediment buildup and will extend life- change furnace filters (more often than yearly)- if in cold environment, turn water supply to exterior off before winter- take a look under sinks to check for any slow leakThis shouldn't take much longer than an hour or so per unit per year unless you find something unexpected, and if you do find something then good job catching it early. 

They could put a small table next to the door by the thermostat. 

Just wondering but how much smart home technology have you added to your locations like video doorbell, smart lock or smart thermostat?

Dryers have thermostatic switches that prevent overheating if the vent is clogged."

Hello,   Looking for a thermostat I can install in a duplex that is converted from a single family home.