Spares, yes... They are pretty cheap. I have at least one spare extended life batt. with me at all times when hunting on foot and have one or two more back at the car and I can charge the batteries off the car, or can use a wall charger I bring with or can hook up to a USB port on a computer to charge if I end up somewhere that's feasible for some odd reason, etc. I'm a big believer in redundant options to keep the electronics going...
I'm also the guy that only uses the Energizer Lithium AA's batts rather than alkaline becuase they work much better in low temps and hold more power and are much lighter and every battery that I take gets hooked up to the volt meter on the multimeter to make sure I'm packing fully charged batteries before I go, etc. I've had too many friends who pulled their headlamps out at midnight starting for the summit only to find their batts were dead and they didn't have any spares. Back when I was jumping we were pretty diligent about making sure switches on electronic equipment was taped in the off position until use and spare batts were stored in such a way that they wouldn't drain as the radio might be only way you could contact 'civilization', etc. Just been drummed into me I guess, for better or worse...