Others certainly have more in site than I would.
But I would think before any one can answer that would need more information like current truck population your are servicing and other things like average income currently being produced by service tech - separate road vs shop (shop folks tend to work on new equipment get ready, rental fleet & used reconditioning (ie in house billings) and those units that the road tech don't want to work on in the field - lol), etc. etc. etc etc..