What are the safety demonstration time-constraints?
I haven't heard of any regulations about the length of the safety demo, just the content, which is pretty much as you described. However it's in the airline's interest to keep it as short as possible. The aircraft cannot take-off before the chief of cabin notifies the cockpit that the cabin is ready for take-off. The cabin is ready after all passengers are on their seats, safety demo completed, galleys secured and hand luggage stowed away.