After a Log and Transfer, and storing the files to a back-up hard-drive, I deleted the footage thinking that it would give me full memory life back (I'm shooting 1080/30p, FH on an HDR-AX2000 w/ 16 GB cards). The initial life is about 2 hours, but after the offload less than an hour is restored to the card.
What am I doing wrong here? How can I get those full 2 hours back?
There's no special setting to determine card capacity or anything else when you format. Go to (on most cameras) Menu-->Others-->Media Format. Do not format on your computer or manually drag files to the Trash. Note that depending on firmware versions the capacity of the formatted card may vary but not by much.
After you format set the record format of the camera, also in the OTHERS menu. The 1080 SP formats have the lowest data rate and will give you the longest HD record times but the HQ formats yield better quality. If you really are losing an hour of card capacity the SD card may be bad.