Kevin, remember that back in steam days railroads had large shop forces including boiler makers and getting a loco in service to haul a train could take precedence over worrying about a future repair. Leaking stay bolts and tubes could be bucked up by the roundhouse shop force overnight and class repairs were probably scheduled somewhat conservatively. That said, the large railroads didn't recommend fast fire up on a regular basis. I have a Santa Fe fireman's manual that specifically mentions how much a hot boiler expands over a cold boiler and also specifies when and how cold water is to be introduced into a hot boiler in order to minimize the thermal expansion and contraction of firebox tube and side sheets. They understood proper procedure, but sometimes they needed to break the rules.
I witnessed a particularly egregious example on a tour to Cuba in 1981. We arrived at Puerto Rico Libre and nobody had told the mill that a tour was coming and all steam engines were cold when we arrived. They said not to worry and put shop air on the blowers, lit the oil burners and had two engines running for us in less than an hour. My guess is, nobody cared about the consequences since it was Fidel's engine! They got paid whether engines were working or not. Pay in Cuba was under $20 a month and a joke we heard several times was that Fidel pretends to pay us, so we pretend to work!
Michael Allen