Depending on how often diesels are run depends on how often they need repairs. Sometimes it can be every 5-10 years between heavy repairs, sometimes a cylinder or two needs to be changed due to worn gaskets, piston rings, etc.
Steam required daily care of a shop crew, a diesel requires a few hours per day usually. Instead of a crew of 3-4 to care for a steam engine per night in a roundhouse, 1 guy can tend to 4-5 diesels per night outside over a drip pad. Shop crews today are much smaller than in the days of steam.
Here in the states, steam could go faster than diesels, but reuired more maintenance as such. Even today steam could still run faster than freight diesels if the track is good for high speed.