They do die slowly. Reduced vapour, reduced flavour are the symptoms. It still heats up and appears to get to temp when dry burning but it heats up slowly. Time for a new coil. My coils never pop, they just die slowly. One to two weeks usually using Kanthal.
I'm led to believe by the literature and remarks elsewhere by material experts that the alumina layer is compromised over time. Excessive heating or cycling accelerates this. Forcing output when there's buildup would be an example also. This applies to perfectly uniform strain-wound coils as well.
Me personally, I like to swap out most single wire <25W single-coil at about 4-5 weeks, or when they start to lose their metallic lustre after a dry burn. This could be after just a a week or two depending on how hard you drive the device
relative to the [coil]
mass and of course how complex or dirty the juice recipe.
Higher mass and multi-wire, like tensioned micro parallels, can last much much longer. I've had folks come back at more than a year with these comp devices firing solidly and very cleanly with original wire and wicking. I'd note though that the latter were all using ceramic fiber Nextel (RxW) woven wicking, an application (t.m.c.'s and Nextel) which I introduced on this forum some years back...interestingly on the <15W devices that were common then. Clean dependable operation was precisely what I was looking for.
Should note here that I use a technique to preserve strain winds using micro droplets of water to clear accumulation using very low voltage, i.e. barely visible heating. This helps maintain the metallic gray aspect of well developed alumina for the short term. However, I suspect the rapid cooling can contribute to disrupting the alumina layer. So this type of cleaning doesn't lend itself to really long term use. High power winds I like to replace every couple'a months regardless to maintain best performance.
Best of luck all.
