I'd just laid out a big bed of "Rapid-Set floor tile adhesive" over most of the downstairs loo, with all the limestone pieces cut and ready to lay, when my neighbour appeared at the door in a state. Veterinary emergency coinciding with a car crisis.....long story.........but could I rush him down to the vet. Twenty minutes open time on the adhesive. If it sets, it's an absolute pig to remove. It's quarter of an hour round trip to the vet. "Come on then Roger, we'd best get cracking...." Only I couldn't crack on too much as there was a friend's rotavator in the back of the van, not lashed down, and if that fell over there would be petrol everywhere and complete chaos.
Anyway, I got back just in time, the tiles went down without any great drama, and I was able to clean up buckets and tools before the adhesive set. Phew.