If the market dictates a hike in rents, then in that case it might be better to even let the tenant go if he doesn't like it, maybe having some downtime between tenants, but having more history to back a higher value of the property for a sale/refi.

I take any downtime that I have abroad (generally 2 weeks/ 5 months) to travel to the states to assess properties, but still find it is very hard to truly get a sense of the local market.

Yeah you really have to call around or have a tenant rep broker working on your behalf checking around and seeing what is out there for sites and rent rates.You have to compare where your existing customer base is, what you pay in rent, and annual sales and profit generated, costs to move, downtime of sales to your business,etc.If the analysis shows market rent is 20 a foot for space like yours in the area and you are paying currently 12 then even with an increase you are likely doing better than if you moved.

There's no down time like SFH. 

This purchase was motivated by the failed $10,000 turbo unit in the old machine, and the pressure to install 170 sewer systems per season means down time is not acceptable.In addition to the costly gear, the indemnified crews have a certain amount of pricing power over any client that needs the work done.

My job offers a lot of down time, and being the restless person I am, started looking for avenues to spend that time efficiently.  

The fact is they have a contracvt with you for a certain period of time.The reason for leases is so that you dont have a vacancy in the middle of winter when it is much harder to rent.In my opinion, I would negotiate with them regarding a fee to cover:  ANy down time in rent - about a month, advertising, cost for you to run background checks and do showings, cost of preparing the new lease, cost of move in and move out inspections.=, cost of you time screening applicants and answering all the questions over the phone, cost of preparing return of security deposit and taking new deposit,   cost of a locksmith to chance locks,  all in all  it should be about 2 months work of rent.The tenants have no idea what it takes to transition property to someone new. 

And you have downtime between deals.

Fast forward and that down time is practically forgotten now.

I also highly recommend the podcast, it's a great way to make any sort of downtime useful (commuting, sitting on the T, etc)Good luck!