Just did a timed test.
One swab burned for about 50 seconds with what seemed to be close to a 4" flame. For the last 10+ seconds the flame decreased until it went out. Burning time at least 60 seconds.
Becton Dickinson #326895, expiration date of ? none shown.
Listed as Thicker, Softer.
Can't say this is what I used in the past, but they are what I have in my kit now.
I imagine with any excess alcohol squeezed out, the burn time would be less, might also decrease with age.
However, plenty of flame to ignite TP or other combustables to start a fire.
Someplace on this site I have a post about FSK in a Can Keeper, or something to that effect, with a modified version of a FSK.