Good point on the mass availability.

When there is a specific agenda or goal to the meeting, I am in support of the meeting. If a brainstorming or thinking session were created and then no progress towards that was tried during the meeting - I would be a bit annoyed.

Thinking time is good. It can help to cleanse the head and bring forth good ideas to try. Maybe most of the ideas will fail - but at least they would have been given some thought first and then tried. In the end, maybe all of those trials would lead to a successful venture. The successful venture just may be due to the effort of trying and thinking and could have been the evolution of one of those ideas from a thinking session.

If nothing else, the session would be fruitful by helping you to relax a bit.