Shortened recording times typically come down to the batteries that you're using.
We only recommend using NiMH rechargeable batteries OR Energizer Lithium batteries to get the best performance and longest battery life. In the cold, use only Lithium batteries as those are not as affected by cold temperatures. The Lithium batteries are not rechargeable however which makes the NiMH good to have in your battery arsenal.
Alkaline batteries are not ideal for digital cameras especially for video mode. Alkaline tend to have voltage drops which can cause the camera to go into auto-save mode before shutting down due to "low" batteries. This is why we only recommend using the NiMH rechargeable or Lithium battery types.
If you haven't already, please be sure to try out the recommended batteries. Please note that new NiMH batteries, need to be charged before use. They do not come charged out of the packaging.
Also, since sometimes mystery data can be taking up space on the SD cards or internal memory while still registering 0 files, please check under properties (PC) or disk utilities (mac) to see how much memory is available. If there is not enough available memory, you will need to reformat the card in order to free up the space.
If you are using a Mac to download and delete files, make sure you delete the files from the memory card AND the trash can before you disconnect the camera from the computer. If you do not do a complete delete, then the card will show ‘0' files but the space will not actually be cleared.