So far I've gone through two carts with stock filler material. I just used them until they got grungy looking, then took the filler out, washed it, dried it and reused the filler until it got "too used". I don't want to call it melted because that brings up a different image than it really is....its just, well, not new-ish anymore.
I have settled on using a 90/10-ish ratio for PG/VG Dekang/Humco and it has been working fine for me. For my VG homemade stuff, I've been cutting it with PGA to match the viscosity.
My 801 atty based units (Stick V3, Minipipe, Penstyle) all love the blue foam, as does my DSE601 and e-cigars. Both of the latter use large sized carts which are close to, but still smaller than, the XL carts. I can't seem to find a filler mod that runs in these XLs.
With my ego setup now, I use it in a Heavens gifts ego lanyard. So it sits cart up while I'm using it. If I am going to set it down for any period of time, I flip it cart down in the lanyard so it won't leak. At night, I disconnect the battery. Since starting that routine, I haven't had a single leak.
I found that leaving it standing up or laying flat with the battery connected for more than a few minutes will get it to leak. Disconnected and laying flat, or connected and laying with the cart end inclined down, no leaks.
It is definitely a picky PV. But it's soooo much nicer than my 510, and noticably better than my 801 type gear and e-cigars, as far as vapor production. In terms of battery life, it beats them all.