Just spotted this. Not something I'd considered, I suppose it makes sense that it would be rougher/nastier with higher nicotine content.
Do you guys mix your liquids at all? Think something like vanilla/tobacco could work.
Coils is up to you, some will say a week, I replace maybe once a month, it depends on how much you puff as to how long they last.
Liquids I have mixed, people rave about Heisen as a liquid, I find it nice, but it can be overpowering and even if the unit is in your pocket, you can still smell the blackcurrant notes, so I have taken to mixing it with apple.
If you haven't tried Heisen, think of those hard blackcurrant/liquorice sweets, with a menthol tinge.