LinkVisitor 3.3 is hanging Rated 5 out of 5 stars

LinkVisitor 3.3 is hanging for 30 seconds or more when I try to “Mark Link as Visited”. But not every time. It seems to consistently hang at times, and doesn’t hang during other sessions. Quitting Firefox doesn’t help. Is my history file for LinkVisitor getting too large? I regularly clear out the Cache, Session Manager Saved Sessions, and Tab Mix Plus Saved Sessions. No other problems with Firefox. I only need links to be marked as visited for 10 days. It would be nice to be able to have those expire after 10 days. if that would help keep the file smaller, if that is the problem. Firefox 5.0.1. OS X 10.6.8. Mac Pro 2X-Quad-Core Intel Xeon 2.8 GHz MA970LL/A.
Memory: 10 GB ATI Radeon HD 2600 XT

Dec 30, 2011 update: I find that every week or so I have to "clear recent history", but choosing to clear everything except for the last 10 days doesn't work. Only clearing all history for "browsing & download history", "all session browsing history", and "cache" will stop the hangs. After clearing all history for these 3 items the hangs go away and firefox is zippy again. I would like to keep only the last 10 days' history, but that doesn't seem to work; it still hangs constantly after clearing all but the last 10 days of history for those 3 items.

This review is for a previous version of the add-on (3.3). 

The likelihood to (apparently) freeze is dependent on the number of unvisited links and the overheads involved in adding links to the history, which appear to be getting higher.

LinkVisitor adds links to the history, so they appear as if they'd been clicked on. Standard history setting will then apply.