I think not only static but handheld flames and oillamps should have an increase of lifespan, sure torches are easy to made, still they burn down ridicoulus fast and seem to dim and reduce its light given off allready before its half burned down.
Could torches aswell be manipulated to increase their lifespan?
Maybe creating different types of torches, a really bright shortliving torch, which burnes even brigther than the current torch, but does have the same lifespan, than a torch which has cloth wrapped around it, upgrading the lifespan to three times as normal or maybe a torch that does not infact burn down, but can be "filled" up again, maybe with pitch, burns twice as long as the normal torch, but can be reused everytime.
A clothtorch would obviously need cloth in its production and the refilling one needs iron, to create an "iron" head.
To the oillamps, generally I think increasing its light giving off might be a nice idea, after all it just gives off the light that a normal glowing artefact gives off and there is a difference between a glow and a burning flame
an increase of burntime would be nice aswell.
I can't say much to candles, never tried them.
An increase for all the static holders would really be appreceated, maybe not only them, but the possibility to "increase" its usefullness, maybe with either overfilling the static holder, oillamps give off as twice as much light, or restocking it, say for exampel as soon as one torch burns down another one will be taken from the holder "storage".