Hijack a bit, intermittently my wick gets "snapped" into 2, well of course no snap sound but it is broken up into 2 in the coil, I will get a dry hit after 2-3 drags and I would know that the wick has snapped again.
Issue is it doesn't happen all the time and it happens randomly on 2 tanks. I figured it's a user problem here.
Other than that, when the wick is right, I change like 3-4 days once.
Had that problem when experimenting with coils to overcome hot leg problem (see my thread on Hot Legs).
Found that when coil too long and thin (venture a guess 26g 9-10 wraps at 2.5mm diameter), the problem you described was common place. Hard for wicking of juice to catch up with the drying at the center of the coil.
More wick, more juice, shorter coils perhaps?