Stability and Alteration Dual Casting perk effects stack rendering its duration to 198 secs, if cast with both hands.
Understandably not recommended for stealth. Magelight may be preferable in these situations as it doesn't constantly reveal your location.
NPCs will comment on the light if you approach them with it active.
Interestingly, in the Dragonborn add-on, when entering some Black Books where dark areas can inflict damage, this spell, and Magelight by extension, has the same effect as using a torch in that it can protect you, so long as it is maintained.