Facilitators: how do you account for time stretching and compression?

Say you are planning a 4 hour workshop. You have 10 sections in your agenda. You know some parts take exactly 5 minutes, and other parts vary a lot depending on the group you’re working with. Some parts can be stretched, and some can be compressed, e.g. if the small group discussion is going well we can take 5 minutes out of the tea break.

How do you account for these timings in your planning? I know it is pretty common to work this out by feel, improvising in the moment, but I’m wondering if anyone uses a more formal system?

Here’s a formalised approach I’m playing with today:

The agenda has 3 chapters. After the first chapter, we’re either running ahead of time, or we’re behind. So the following chapters start with a “time-sponge”: we can stretch or compress it without any harm. The ending time is also a natural time-sponge: I always like to be out of the room on time, and I’m happy if we finish a bit early too.

In this case: the doors open at 9am. The first chapter takes 70 to 100 minutes. So our first sponge (the tea break) could start anywhere between 10.10 and 10.40.

Chapter 2 is 45–70 minutes long. If we’re moving slowly, I’ll squish the sponge to save ten minutes, so it’ll take 60 minutes (finishing 11.50 at the latest). If we’re quick, I’ll soak up time with a longer tea break, pushing the chapter length out to 55 minutes, so we’ll finish at 11.05 at the earliest.

Chapter 3 is 60–90 minutes. The “Team Challenge” discussion is my time sponge here. If we’re super snappy, everything moving like clockwork, I’ll add 20 minutes in here, and we’ll be done by 11.05+60+20 = 12.25. If we’re sluggish (AKA chatty), I can take out that 20 minutes and we’ll still finish on time at 1pm (11.50+90-20 = 13.00).

Does that make sense? Is there another way people solve this?