Fill early and often is my motto. I hate the dry puff.
Also though if the coil is bad, change it. It may pollute your juice, and that is something you don't want. I always get rid of my juice if the coil is going bad (IDK that it is, but possibly).
If you want a new flavor you can remove the juice inside (note, do not put back in original bottle it may pollute your nice, unused juice. You can also soak the coil in vodka or everclear and the rinse it and it probably won't taste like the juice you were using and once it dries out, you can use it in a different type juice,.
Mentioning all this as you seem to be thrifty sort. I got no problems with that frankly. But, FYI
Anna