As pointed out above, the grid heaters have been around for a while. Glow plugs have not.
Also, there's no issue with corrosion on the grid heater bolts. A loose connection at the isolator, sometimes caused by a stuck solenoid, melts the bolt and sometimes the nut and part of the bolt makes it into the number six cylinder.
The fix is quite simple: Disconnect the lead to the solenoid at the battery. With the grid heater inoperable the bolt can't melt.
Lastly, people are putting 400,000 to 500,000 on their roller lifter Cummins with no problems.