It must be the nicotine, I changed my mod the cotton and the wire. I've been vsping 3 days now without rewicking when I last used the old nicotine it was 12 hours before I had to rewick.
I'm sorry I would usually read every page but I am finding it really hard to concentrate at the moment for certain reasons. Have you changed to a juice that has a lot of sweeteners in? They gunk up coils fast!
Please don't give up though mate, you have managed it for 4 years and that is a real good achievement!
Some people don't recommend it, but have you tried taking wicks out, a gentle dry burn, then re wick? If they are newish coils I sometimes even give them a careful drip of water while doing this, please DON'T do this if you don't feel comfortable doing it though. I find it helps get the gunk off and can re wick and like a new coil