as much as it seems practical you must remember these work horses can be on the road for over 15hrs a day stop start slow fast moving vehicles...

if you have any knowledge about vehicles....

say have a brand new fleet of "branded" 21 Angel or X10 dedicated to the route after 30k miles the same parts will sadly fail

like a timing belt on a car to be changed every 60k miles

if you have 12 or 15 brand new buses all doing the same route the mileage will be similar so when it comes to the milestones they fail or need to be sorted out...

interestingly in a petrol/ diesel car there is 200 different moving parts

in an electric there is about 20