I've taken part in 3 - you've got to be careful who is in the group as one floundered - one member sat on our moleskine books for months as they arrived until they had about half of them, not responding to emails, before finally saying they couldn't take part after all and having done no work in them.
At the end another member said she had arranged an exhibition and could she have all the books - she didn't return them The organiser got no response from emails or letters..
- total disaster
Another stalled at times due to personal problems people had, but the group kept in touch and it finished as planned, just a little late.
Another ran brilliantly. We had a group blog
, everyone was totally reliable and it was a great success. We sent all our books to the organiser to do a talk about the project/exhibition and all came back safely.
I've just agreed to take part in another, again with a group blog.
This time sending a postcard (sketch/painting plein air) once a month from a walk. The first cards go off at the end of the month and it will last 14 months.