Memory status with 16 GB card?

[Wyshwood]

In a few weeks I have a 2 hour concert to record multitrack. 8 tracks at once.
When the whole thing is finished and I want to transfer WAVs to DAW, how much memory needs to remain on the card to enable me to convert the recordings to WAV in Audio Depot? I am assuming the recording takes X amount of memory and the converted WAV takes up a fair bit too.
Thanks in advance for any advice given.

 

[Wyshwood]

I'm experimenting with this now, because no one seems to know.
First results, not good. At 24 bit it errored out at 38 minutes, which is useless for a 2 hour event with a break after an hour, so I've dialed it down to 16 bit to see. I'll post the results later, as time allows.