I use one of the first GoPro's that came out, obviously not as slim as the later models, but 1080 HD quality, 32G card. Later ones record at a higher res, 4k and use a 64gb card.
Carrying a spare battery or two is the way to go, swapping them out during pits tops, just keep it on standby mode until you need to record the lane your on etc. I can get a half day on one battery using it this way. So not an issue for me.
I think you get just under ten mins. record time per GB when using the 1080 setting, more if a lesser recording setting is used, this would equate to 320 mins. approx. using a 32gb card, plenty if your only recording the green lanes your on.
But, think I may fall into the TT bracket