They run for a long time after starting now, which is probably why they fail so quickly these days.Times have changed and glowplugs also glow for some time after starting.
I hate these modern M8 glow plugs, as they snap for fun.The biggest issue with glow plugs on the 2.7 is they snap when being removed, serious amount of effort to get them out if they snap.
Oddly the PSA DW12, uses the same plugs, but don't stick in the way the TDV6 plugs do, which is weird.