I have the Camelbak Blowfish, it must be almost retro now (must be knocking on for almost ten years old?), replaced the bladder once in that time.
The Blowfish easily contains a full 3ltrs of water, a waterproof jacket, 2 tubes, way too many tools, phone, wallet, keys etc etc.
My top tip is to clean the bladder using Milton sterilising fluid every now & then to kill off any mould, one of my mates swears by Steradent tablets (you know, the one for cleaning dentures
), will give the freezer trick a try too now though