Calor Lite 6KG

Does anyone have any idea how long these should last, i know its all subject to use!

I replaced my 6kg bottle last month and have done the roughly 6days on gas only, cooking once a day, boiling the kettle several times a day and obviously the fridge has been permanently on gas for the entire time, have just checked my bottle I'm convinced its nearly empty again. Does anyone have any idea what the full and empty weights of these bottles are? and whats an average lasting time per bottle in terms of days used.

Obviously I shall also consider the leak possibilities also!

thanks