It all depends on the mAh rating. A battery is not a battery
Check out ebay for some Duracell rechargeable with around 2500mAh and they should easily last you a week session.
Look for the new style rechargeable battery which will hold the charge for approximately a year, as opposed to the 3 months of a 'normal' rechargeable battery.
To be honest, unless you buy pound shop specials, any AA battery will last longer than the rechargeable boat batteries.