I have heard the same results. There are trucks out there still running the factory glow plugs and controller and have never had an issue. I have seen posts that they can't keep the glowplugs working a week.
The 6.9 controller that screws into the back of the drivers side head is a simple controller. However when it fails, it normally fails ON. Which, powers the plugs constantly until they burn up. There is a replacement out there for the 6.9 that works more like the 7.3 controller. Have not heard much about them though.
The 7.3 controller that is on the rear of the intake, or relocated if a turbo kit has relocated it, is a more complex controller. It actually senses the current draw across the plugs to gauge how hot they are. The compare the voltage to the plugs, to that across the Zig-Zag metal strip on the controller. When these fail, they fail safe, or off. Which is good and bad, you do not burn up plugs, but if you have a failed plug or two, you get the short cycle and no start. I have not seen anything "official" many on here have seen the factory controller seems to work best with the Motorcraft/Beru plugs. Not the no swelling/breaking, but seem to work more reliably with the controller, they have more consistent results. Others have used other brands and styles with mixed results. Some good, some bad.
There are other options for plugs, not stock plugs. There are the Wellmans that are supposed to be self regulating. I have heard mixed results. Trav used them and I don't remember him saying anything bad about them. Others have used the AC/Delco plugs for the 5.7L diesel. These are a 12 volt plug rather than a 6 volt plug. Remember, the factory plugs are a 6 volt constant rated plug that has ~12 volts applied to them so they heat up fast, which makes the WTS Cycle shorter. The advantage the AC 12 Volt plugs, is you could turn them on with a switch and leave them on and they should not burn up since they are designed to have 12 Volts applied to them. Bad thing is, it takes them much longer to heat up, and you have to use a manual setup. Trav used these for a time in his current truck (86 6.9 Dually), and when it was cold, it would take almost a minute (a real 60 second minute) for the plugs to be hot enough to start the truck. I think for a time when he had these, he actually put an on/off switch on them instead of a momentary switch because they had to be on so long. Now, he has gone back to ZD-1 Berus and a momentary push button.
Other factors that can limit plug life is physical damage. Highly advanced timing can EAT glow plugs. One member on her who has a Mercedes diesel advanced the pump 5 degrees because he was running WMO. He would have the glow plugs starting to be eaten within the first day of them being installed. He backed the timing off, and the glow plug damage stopped.
Now, fast forward to the newer computer controlled trucks. The PSD's. These actually have a true intelligent controller, that are run by the computer. These trucks seem to last much longer. On my 03 6.0, it runs Motorcraft ZD-12 plugs. They are still the factory plugs at 137,000 miles. They are more carefully controlled, and if one fails, it will set a Check Engine light, and report to the ECM what plug is bad. I have not read on the newer truck owners going through glow plugs like the older diesels.
I would say, if everything is in good working order. The controller is in good shape, the truck start well, and the batteries are in good shape, and the truck is in the proper timing range, they should last for a fairly long time. No necessarily "forever" as they do wear, but they should last longer than a day or a week. One thing most people do, and I recommend this also. If the plugs are "old" or have a lot of miles on them. If one fails, replace them all. They are all the same age, and have seen the same conditions. I have a co-worker with a Duramax, and he was looking for a glow plug earlier this week because one went out and set a CEL. This is the second one he's had to replace. I feel if he had done all of them while he was in there, he would not be doubling his work, because they would all have been new. On my truck, when one eventually goes, I will buy 8 Motorcraft ZD-12's and replace them all. The remaining "good" ones will go in the tool box for spares...... Fortunately for me on the 6.0, they moved the glow plugs back outside and can be access by just removing the glow plug buss bar, and remove the plugs. They are not under the valve covers like the 7.3PSD is. I would defiantly replace all 8, or at least the 4 under the valve cover I had to open, and I would more than likely replace the valve cover gasket and wiring harness under there too, especially if everything had been on there for awhile.......
