On the 'Page, our father-forum, a new 60G was connected to a fully-charged 12v battery, with attached battery-charger to maintain full charge, for 8 hours - the plug glowed brite orange\yellow over the full interval, no swelling, no deterioration, no lessening of intensity along the length of the probe - only problem with the 60G plug is the slow-heat property, requiring extended glow-time - that test was extreme, as the oem fusible-wire glow-harness is spec'ed to drop applied voltage down to ~10v at the plug terminal, aiding and abetting the extended glow-time requirement