Additionally, you want to ask how much remaining life span was on the unit so as to know whether the replacement was fair.

The life span of this type isn't as long as shingles. if they are 3/12 or more then I would go ahead and do just the repair.

Kona has a special place in my heart because I was a student and staff member at the University of the Nations on and off over a span of four years from 2013-2017.

They are typically a bit more expensive up here than asphalt shingles but have a longer life span.

Water heater sizing or life span?

People have short attention spans.

Is there any reason that would prevent me from repeating this process multiple times in the span of a few years? 

Besides looking at cost you need to look at life span. 

You have a few different materials used in that foundation, i agree with @Russell Brazil on this, yes there seems to be some " handyman" work done, but nothing bad enough that can not be fixed with some jacking up and repairing certain areas. the contractor probably does not want to bother with it ( who knows, he may want the property himself after seeing it) so he is trying to make you think there is a ton of work to either give you a high price or hopes you will walk away so he can grab it. the roof, plan on installing a new roof, shingles look close to their life span and not because of the color, look at the gaps between each tab ( the views from above show it best) when they start to widen up that means the shingle is drying up and close to the end of it's useful life.

Attention spans are short.