I think it depends on your burner. Some are more efficient than others. My new burner, the Bayou Classic patio cooker, is much more efficient than the wal-mart-special turkey fryers that I'd been using.
I have 4 tanks total and I always keep spares...
MOSS HOLLOW BREWING CO.
Aristocratic Ales, Lascivious Lagers
Scottish 80/- Sweet Stout Roggenbier
.primary | bright:
98: Moss Hollow Soured '09 72: Oude Kriek 99: B-Weisse 102: Brett'd BDSA 104: Feat of Strength Helles Bock 105: Merkin Brown
.on tap | kegged:
XX: Moss Hollow Springs Sparkling Water 95: Gott Mit Uns German Pils 91b: Brown Willie's Oaked Abbey Ale 103: Merkin Stout
98: Yorkshire Special 100: Maple Porter 89: Cidre Saison 101: Steffiweizen '09 (#3)