After a few months of basically chain-vaping and carrying it around in my pocket, I started needing to press the button really hard and/or several times to fire. And sometimes it would stick until the 10 second time-out, which, without air-flow, would kick-start a rapid descent to burnt flavour and a rebuild.
I tried to pull it apart for cleaning but my soldering gear isn't here (only need to de-solder 1 wire for disassembly), so i put it back together and into the ultrasonic cleaner.
Tap water (figured the chlorine might clean some) and 10% PGA, turned the Pico (battery cap off) over until the air bubbles stopped, 30 min, then another 30 min on the other side in 100% PGA to de-water and 'super-clean' (being a DIY'er I have access to litres of PGA ), left it sit overnight and VOILA! Just like a bought-one