Yeh I use a 21700 in it mainly - but I havent really gone above 70W as I love the coils it comes with - for smok they are amazing. The S1 lasted over 20 days - but I had to take it off to review the S2 and that had done 1001 puffs last time I looked - but had a different atty on there for a bit - and lost the puff count now. But not a single leak, dry hit and the coils are lasting ages.