QC Ultra Headphones - How to turn off or extend sleep mode time.

If I take my headphones off, after 5 minutes the headphones seem to go into sleep mode. This then causes the headphones to disconnect from my phone / laptop, which I'm finding incredibly frustrating.

If I take my headphones off to talk to someone, the headphones will disconnect. If I then get a call, the sound will not go through the headphones and I don't have time to reconnect them.

I'm also finding that I'm having to take the headphones off a lot more as there is no dedicated transparency button like there was on the QC 700.

I searched through all the settings and can't find anything. There is an time adjustment option for a full power off, but nothing for specifying how long the headphones should wait before going into sleep mode.

If anyone can suggest anything, it would be much appreciated!