Welcome to Android Central! Is the camera set to save video to Internal Storage or the External SD Card? If your Internal Storage is already pretty full, then that will limit how much HD video you can take. If you have a big external SD (like 32 GB), that should give you more room.
There is apparently a 4 GB file size limit in Android, so that might also limit the length of your video, but a 4 GB 1080P video should still be about 30 minutes.