Since you have multiple houses, you can buy cylinders of it on ebay, if you think supplying it yourself to the technician will be cheaper overall. 

I use landlordlocks.com, I have a control key that removes the cylinder.  

You can draw all the parallels to the last crisis but the truth is as they quote in the following article, "history doesn't repeat, it stutters":https://www.atlanticcouncil.org/blogs/new-atlanticist/can-we-compare-the-covid-19-and-2008-crises/We have a tech economy that is firing on all cylinders. 

I had the same problem where I have to check the Taps, Sinks, Valves and hot water cylinder and all other pre-tenancy plumbing checks.

Or I might forget to carry revolver on an empty cylinder.

Now I am changing locks at another property and I am thinking to key the cylinders the same.

You change the cylinders, not the entire lock, when you need to change locks.

I do have locks with interchangeable cylinders, so at turnover time, I just swap the cylinders, rather than the whole lock.If the property is far from where you live, this next idea may not work for you. 

If my brain is firing on all cylinders I would recoup the $1800 lost in 6 months by the increased rent. 

Is there a window in the door that a dumb criminal could very easily break, reach in, and turn the knob on a single-cylinder deadbolt lock to open the door?