I believe that isopropyl alcohol can degrade plastic or rubber gaskets and washers. When I use alcohol I use cheap vodka.
I clean my iclears and kanger pt's pretty much when I notice a decline in performance. Usually it's a much tighter draw; sometimes a drop in flavor. I'd guess I normally get 3-5 tanks use, depending on the liquid.
My routine is to take em apart, rinse with warm water, towel dry just a little (carefully so as not to dislodge anything), dryburn, and then soak in vodka at least a couple of hours. Then rinse, let sit overnight, and good to go.
Sounds like a lot of effort but if I can time it so I clean 5 or 6 at one time, it takes about 20 minutes and then I can forget about it for a couple of weeks. Not too bad.
And, pretty sure you can get away with just rinsing most of the time, if you don't want to go thru all those steps, though watching all that gunk burn off when dry burning makes me think it's worthwhile.
I've been using 5 iclears and 2 pt minis with original heads for 4 months with no noticeable drop in performance. (and I'm sure rebuilding is still the most efficient route. I just haven't taken that step yet)