Wondering if anyone knows how often you should change the glow plug? I have had my EX6, for 13 months and do a lot of long cooks, a lot of briskets. The EX6 came with 2 replacements and I have never changed the original. I am afraid it may wear out in a middle of a cook? Manual says you get a notification, but does not indicate how long you have after you get the notification?