A 32oz. bottle should last you a while. Normally you only need 3-4 pea sized dots to prime the pad, then 2 dots per panel after. I've had the same 32 oz bottle for 2 years now.
i throw everything i have in the back of my pickup and i never had a problem with any product going bad. although my cover is white (less heat transfter), and it has some leaking in the corner for ventilation..