Most cost effective HVAC A/C maintenance strategy for buy & hold

[Bryce Carroll]

I'm interested to learn what successful investors with 10+ SF units do for HVAC and A/C maintenance to make the most of their money in long term buy and holds.  You can't make tenants replace filters which will strain these systems, hiring someone to do it monthly isn't cost effective I think.  I don't see a way to force tenants to do it, so I'm not sure its beneficial to take care of the rest of the unit with the filter always clogged.

The options I see that investors have are:

A) Ignore maintenance of these systems and replace/fix them as needed throughout the years.  Probably not the best idea, but if there's a 10 year warranty maybe?.. 

B) Pay for yearly inspections (once or twice a year).

C) Pay for a bi-yearly maintenance which includes cleaning etc.

The numbers on a maintenance package don't appear cost effective to me; if I pay say $200 a year for maintenance, it doesn't guarantee that there won't be further problems, and in 10-15 years I may have to replace these units anyways because tenants aren't replacing filters and they're being killed from the inside.  Or they're just poor units, or poorly installed.  And this assumes nothing is ripped off in the rental, I've had to replace furnaces the last few years from criminal mischief despite the rentals being in good areas.  So this makes me think I'd rather keep that $200 a month and be ready to replace when the time comes.  But I'd love to hear what experienced investors have done to make the most of long term buy and hold investments over 15+ years?

Thanks!