I have noticed that the durations were Essence + 1d6 hours in every case. As for the power of the effect, sometimes it's pretty important. Spirit Strength is fairly explicit:
QUOTE
Spirit Strength
Duration: Essence + 1D6 hours, maximum 12 hours.
Effects: This compound grants the critter powers of Hardened Armor 5, Mystic Armor 5, and one enhanced sense of the gamemaster’s choice.
But in other cases, it's a bit less so:
QUOTE
Little Smoke
Duration: Essence + 1D6 hours, maximum 12 hours.
Effects: This mixture grants the Concealment and Confusion critter powers.
I have no idea how powerful these powers will be when activated, which is crucial for Concealment, and part of the resist roll for Confusion (The critter makes a Magic + Willpower Opposed Test versus the target’s Willpower. The nets hits scored by the critter serve as a dice pool modifier to any action the target takes. SR4A p293).
My intent was to purchase some of these for my mundane character. For most of them, the power is explicit in the description, like in Spirit Strength, or implied in the asscociated spell (Innate Spell (Animal Control) is based on charisma). So, if my 1.2 Essence Street Sam chugged a Little Smoke, and rolled a 2 on the 2d6 roll, how would you suggest it be handled?