Ego-t attys & tanks on Riva batteries are all I've been using for over a month and I'm still using the original tanks.  I guess if they start to leak or do something adverse I'll pop another in. I've got three filled with different flavors and my wife has two with different flavors.  I did lose one atty but so what.  I'm well over the settup cost in savings over cigarettes and can live with that kind of minimal maintenance.  I fill by popping off the botom and dripping right out of the bottle.