Personally I prefer smaller cards and I swap out both battery and card every ~2 hours.
On anything > 16gb (assuming 30fps) the battery is going to be the limiting factor not the card.
I've been burned a few times when I wasn't doing that where either the battery or card maxed out and I missed out on some sweet footage, so now I take no chances and just swap both.
I would recommend getting the remote so you can start/stop it easily without having to get out of the truck (assuming you mount it outside), it cuts down considerably on both battery/card consumption as well as the amount of editing you have to do.
My favorite mount for anything on land or sea is the suction cup, but ALWAYS tie a backup tether to it as well (I won't admit how my of these damn things I've lost)