new topcoll server side preferences will create extra load on server / also creates an error when session times out

Hi Garreth,
I've been asked to have a look at the topcoll format again, theres been a few changes since i last was here, looking good.
However i need to raise an issue about the new server side preference storage.
1) using ajax for every click creates extra unnecessary load on the server, we have 1000's of students and if they were all on a subject that was using collapsed topics, every time each one of them click on a collapsed topic it would send an ajax request to the server creating lots of overhead
Is there a way you can make the server side stuff optional, or even turn off

2) when the session drops or times out, the topcoll ajax will produce the following error:
"Error updating user preference 'topcoll_toggle_1646' using ajax. Clicking this link will repeat the Ajax call that failed so you can see the error: "
I don't know how the rest of moodle handles it as it doesnt really have an ajaxy interface

3) The following error is received when clicking on a topic heading before the page has finished loading, no biggie, just thought i'd log it here for completeness "ReferenceError: toggle_topic is not defined
[Break On This Error]
toggle_topic(this, 1);"