Sometimes I, or a friend, places the wrong buff by mistake. Nothing worse than a friend placing a basket on my coinage at 6pm, meaning it will run out at 3am.
In that situation I would like to be able to cancel the buff at 10pm and ask a friend to place a new basket. I realise I would only be getting 4 hours effect from my first basket, but that's fine.
Another example is when 2 buffs run out 15 minutes apart. I would rather my buffs finished at the same time so I can arrange one swap. In that example, I could let one basket run for the full 9 hours, but cancel the other after 8h45m.
It would be great if there were a "cancel" icon in the building details, near where you show a picture of the current buff. After an "are you sure", the building would revert to being unbuffed (you could change the remaining time to 5 seconds in the code to keep things simple).
Simple and effective.