I found about 5ml left in a 2 year old 30ml bottle of Hangsen VG Original Red, added it to my Boge carto which was about half filled with Hangsen PG Cigar, and had the worst tasting vape I'd ever imagined. I think it went bad or something... Haha...... Funny thing is, I didn't want to throw my carto out so I vaped it all. The PG Cigar has retaken about 90% of the taste now, so my carto can be used for a few more days.