How long does a wick last in an OdyV2? I've had the same wick/coil for over a week and it still seems fine (although I think the guts of my Ody could use a cleaning to get back full air flow). So, I guess I'm asking is it just a change based on taste or is there a set interval in which the wick material starts degrading (I'm still using the wick that came with it)?