Once you activate a boost there's no option to pause it or store it. (Although it would be good to)
This is what I understand about the boost so far.
****Are the prices the same for all?****
Fast worker.
Lasts: 3 hours.
Cost 5 bronze 7 silver.
How is works: The workshop timers runs 2x fast. (You do not see a reduced time, but while active 4 hours will finish in 2 hours) Tinker camp excluded.
Nimble farmer.
Lasts: 3 hours
Cost: 10 bronze
How it works: Timer on crops runs 2x faster while active. (Again you do not see a reduced time)
Harvest Champion.
Lasts: 3 hours.
Costs: 5 silver 15 bronze
How it works: Drop 2x the crops harvested (some drop total 4, when you would received 2) energy drops seem increased too. When active the boost icon is attached to the pop up for cottages and Ivy's hut, but not other buildings.
Gold Miner.
Lasts: 5 hours.
Costs:3 silver 12 bronze
How it works: increases chances but > doesn't < guarantee gold nuggets from sparkling mine.
You have a boost icon appear on the relevant building / crops when activated, and you can successfully activate multiple boosts at once.
Another thing to note: Make sure you have selected the correct boost you want to forge / activate when you get to to forge screen in the apothecary as the fast worker boost (1st option) is always selected. Even if you hit "get" another boost in the screen before.