Just a though. so you can only take a number of burn points a day equal to 3+ con mod. each time you take one point of burn you take level in non lethal damage. now comes the change up, if the burn non lethal damage would heal normal both with magic and without. normal healing would be 1 point of non lethal per level per hour. and any magic healing would heal equal amount of non lethal and lethal damage at the same time.
so without magic healing each point of burn takes one hour to heal naturally. but you can still only have a number of burn points per day = 3+con mod.
now given that some games have it be the 15 minuet adventuring day, if natural healing was available it would not matter, if magical healing is possible it would use up some resources from the party be it a cure spell or a aoe healing some resources is used up.
other games have it be hours between fights,(days does not matter for this) so downtime would matter a bit more, each hour would make it that much easier to fight same goes with magic healing. but the thing is you can still only take an amount of burn = to 3+con mod a day.
bottom line if natural healing and magical healing is allowed for burn damage it does not change how many times a day it can be done.
sorry if it seems all over the place, just trying to put in my thoughts on this as best i can.