It took longer to full heat tha extra can, usually once i saw green, it was good to go, if i used an oil can i usually let it warm up little longer. I did use my rubber caps. Battery life suffered just because it took longer to heat. Other than that, i dont remember a single negative.. I did like having my non spillable prefilled cans.. I also suggest trying their prefilled eo cans. I saved mine for herb filling.