When I want to revive an old coil, I start by removing the grommet, the "smokestack" tube, and any flavor wicks. Then I burn the coil while blowing on it until the coil burns red. Then I add a drop of Atty Refresher from Want2Vape and burn it again until the coil gets red. If the flavor wicks are in decent shape, I put everything back together, take a few dry hits (no power) to resaturate the wicks, then a few puffs that I do NOT inhale, as there is some aftertaste left from the dry burning and Atty Refresher, and then I vape.
If the flavor wicks are nasty, I will put them back on and put everything back together, and then repeat the process with the Atty Refresher while taking pulls off the "smokestack," and put everything completely back together. If the flavor wicks are just too nasty, I will just replace the flavor wicks with a fresh bit of 1 mm silica.
This whole process ends up restoring the coils to like new condition, and it takes just a few minutes per coil. I am still waiting for one of my coils to pop and die completely, but I have not bought coils in months.
I should also note that when I have everything disassembled, I use this as an opportunity to double check the coil and make sure that it is properly centered and that none of the individual wraps are too close or too far apart. I use needle nose pliers or tweezers to make any adjustments that are needed. By doing this, I have actually improved a coil's performance. One coil was so far off center that I kept having leaking and gurgling problems. Once I re-centered the coil, it worked flawlessly.