I use to work just the listed REO's, but I have realized for longevity I needed to start marketing to homeowners direct.

Yes, for longevity, 15 minutes of maintenance/backflushing of a tankless per year is a good idea. 

This ensures the interests will be mutually aligned as they will be married with you through the longevity of the investment. 

It hasn't effected my business model at all ...yet...I am interested to see the longevity of the S8 success.

True success is measured in longevity.  

Being that it is largely suburban makes me question the longevity of the city with newer generations prefering walkable cities.

Not allowing the use of personal wipes, not disposing of grease in the system, and usage of friendly laundry detergent should be enforced strictly to ensure longevity.  

It's not at all unusual to find garbage places built the 1970s that have much worse and chronic problems than a place built with care in 1920.In buy-and-hold, your job is always to pick places that have investment longevity, that can be renovated, in areas that will most likely appreciate.

My PM, who will be supervising the installation, suggested that we go with metal for longevity.

I have a saver's switch on the A/C unit on our primary residence. A friend of mine told me he had asked a friend of his who is a HVAC professional tell him those hurt the life of your A/C unit.I did a search for "save...