for inhouse techs you would want to own more than 10 machines to keep the guy busy and justify his salary
but
dont ask your facilities maint guy to fix the forklift he'll waste time and material working on something he knows nothing about
then youll have to call a guy like me in to fix the mess at an even higher loss than just calling me in the 1st place

also try to stick with 1 brand and get factory training for the mechanic that way he has access to all the diagnostic tools he needs

sum up
if its done right it can save a lot of money
if its not, bye bye profit margin lol