[Piotrsko]

Can't advise on glow plug life, mine in the F250 have lived for 25 years in high altitude cold winter (-20C) environs, 13 years on the TDI, both are daily go to work drivers stored outside Eaten a couple controllers, bunches of batteries, and mildly unsure if the computer or controller monitors failures. Suspect not.
I do know school busses need to crank longer when a glow plug fails, and when they do start run like crap until you get cabin heat. Some times it is a race to start before the battery dies.