I don't try to make a carto last. If it's at all funky or not a good draw, I get rid of it because I love a fresh new carto.
I DIY most of my liquid, most single flavors- peach, pineapple, lemon, etc at about 80pg/20vg. I attributed it to that.
The high VG tobacco cartos- you can't even draw out of them after a few days.