I am very specific in my requirements, frequency of mowing, fertilizing, seeding, watering, etc... and I periodically inspect, either in person or have a trusted agent do it. 

I don't have any so don't know the frequency of inspection needed but definitely look into it.

They're still popping up semi-regularly, but with less frequency.

I didn’t mention that the landlord is trying to make them pay for the repair because they didn’t change to air filter every 2-3 months even though the lease doesn’t have specific requirements for frequency but just “as needed.”

The best advice is to consider each potential applicant on an individual basis, and consider the nature of the offense, the time that has elapsed, and frequency of violation(s).

But researching other Hosts pages, the number of reviews, frequency of reviews, and price can give provide a starting point.

Look up the "frequency illusion"! 

Other than changing filters, what other regular maintenance should be done with ac unit and at what frequency? 

You can keep sinking time and money into a dinosaur that will continue to crap out with increasing frequency, or bite the bullet and replace it.

- blog content frequency suggested 🗓- would you suggest implementing video as well?