What scheduled tasks do you do to your house monthly/quarterly/yearly that more people should do? I looked up a frequency schedule and put it on my to do list to remind me and every time it comes up I'm like I don't need to do that. crap like 'wipe down the walls', etc. eff that.
Drain the hot water heater every spring. We play someone to come out & service the AC & furnace every 6 months.
I've read about these two things and won't do either of them. My AC guy won't even come take my money, says it's dumb.
The bi-yearly HVAC tuneup is dumb!? I have been told otherwise and now I’m not sure who to believe. 
It’s like $100-$200 per year, they change all the filters & take apart my outside A/C unit to spray it out. We have Bermuda grass, which easily gets in the fins reducing their efficiency. Our drier also vents out right next to the AC unit, so one side of the fins gets covered in lint. Having him spray it out helps on electricity costs. Also, with our deal if we need any additional service or new units we get a discount. Our house has the original HVAC from 2005, so when we need a new AC the discount with cover years worth of tune-ups.
You should definitely have your outdoor unit cleaned with that setup. I want to smack builders when they vent the drier next to the AC unit.
The rest of you should be hosing the outdoor coil once a year. Keep the dirt and debris off the coil to help with efficiency and electric costs.
Furnace tuneup? Meh. If it lights, call it good. Just change your filter regularly.