CellBoost or Spare BlackBerry Battery?

I was in Best Buy the other day and as I was walking around, I came by a CellBoost display for various mobile phones. A CellBoost is a disposable battery charger that allows you to get an additional 60 minutes or so of time after your batter runs dead in your mobile device. The Best Buy display didn’t have a CellBoost for BlackBerry but you can get them online and I believe that you can get them from Radio Shack as well.

Being the impulsive buyer that I am, I probably would have picked one up if they had them in the store, but seeing how I was going to either have to go to another store or buy online, I thought about it a little bit more. For $12 or $13 bucks you get 2 disposable 60 minute batteries. The question that immediately popped into my mind was how long will a regular BlackBerry Battery hold a charge when not in a BlackBerry. My thinking the is that if a BlackBerry battery will hold a charge for a least a few months, that I would be be better off just buying a second battery as you can buy BlackBerry batteries for around $20 bucks or so.

Now, If I ever see a CellBoost for BlackBerry in the store, I would probably still pick one up because something has to be said for the convenience of not having to remember to charge your spare BlackBerry battery that is stuck deep down in your laptop bag or in the far recesses of your glove compartment.