7 lbs of propane for one batch seems excessive to me.
I easily brew FOUR, 11-gallon batches using my SQ14 and about 15 lbs of propane. I do 90 minute boils and heat my strike and sparge water on it too. My boils aren't raging but they are nice and rolling with plenty of heavy steam.
One thing I do though is I have a heat shield made from curved 24" sheets of tin that rides half way up the kettle walls, shields the burner from wind and channels any heat that escapes around the kettle into the kettle walls. I think this has something to do with my efficiency.
Next up: Amber Ale
Primary 1&2: 90 Min IPA clone
Primary 3&4: Belgian Wit
Keg #1: White Mosaic Pale Ale
Keg #2: Empty
Drinking: Amber Ale, White Mosaic Pale Ale