You can extend the 24 hr spoil time by mixing in a new alchemical item during that time frame.
Could get expensive, though.
Assuming you can Full Pouch
the materials, what's the most efficient format usage of spell slots to keep one of these on hand? 1 slot per day would keep refreshing the potion until it hits max potency, but would mean having to track daily potency. 6 Slots to make one of each of the 6 materials would give you a max potency potion that lasts 24 hours each time, but (for my character for example), that's all my level 2 slots for the day, and I don't think I can justify 6 spell slots to have one free grenade per day, even if it is a REALLY nice grenade.
Hard Mode: Assuming you can restore a Focusing Flask
using Make Whole
and a CL of 14, would the ideal setup then be 1 slots per day to ramp up 1 potion, 3 slots to full pouch copies of it to toss in the focusing flask when needed, and 1 more slot to fix the flask after? The focusing flask isn't an alchemical item, it's wondrous, so we probably can't Full Pouch the final version, but we can definitely Full Pouch hybridized ones.