At least one means of starting a fire should always be on your person, not in your pack. Butane lighters need to be carried in your pocket near your body to keep them warm but be aware that the fuel button can be depressed in your pockets, front pockets seem to be worse about this.
Always carry a backup and in cold weather always carry a backup to your backup. Matches are lightweight and easy to pack as is a striker style fire starter. Lifeboat matches are always a good bet but you can also waterproof strike anywhere matches with a little melted wax; carry them in a waterproof container. Cotton balls or dryer lint mixed with Vaseline make good fire starters as does charcloth. You can also get a magnesium block that you shave or spend money on stuff like Maya Dust from Light My Fire. With disposable lighters, you may have to remove the metal shield on the front to get a good spray of sparks. Having a couple of candle stubs with you can also help get a fire going.
On a side note, when I go paddling in cold weather I also carry a small road flare for emergencies. If you've ever inadvertently gone swimming in freezing conditions you know fine motors skills are the first thing to go and trying to strike a match is almost impossible; with the flare you can pile up whatever wood you find and shove it in the pile to start a fire quickly and easily.
ETA Example of small flare for outdoor use-
Orion