This is a problem that I've been having for quite some time now. I've gone to a dedicated box. Persistant connections is turned off. Default aged threads is set for 6 months... (even that is too short for my board... it's just the way it has to be). My host has set max connections to 1000 with a time-out of 70 seconds. The next step is to split the site to two boxes... one for the database and one for the web frontend. We hope this will allow for more breathing room as well as allow for monitoring scripts to be written to catch the early stages of this issue and take precautionary measures before it goes into critical mass.
I'm told that the problem is in the software itself. There seems to be a failure in closing connections. They get stuck in what can only be described as a loop... continuously trying to connect even though the connection has been "closed" on the user end. Evidently this has been an issue for many, many versions of UBBT and has yet to be resolved. I've even heard that it has yet to even be acknowledged by InfoPop.
Regardless... I am stuck with this as there are no guarantees that porting to another software will be successful. My database is too large for me to simply move it to another software and/or just start all over again. I've had to create a back-up site for when this "affliction" hits us... which is every single evening. Thankfully, I have a host who monitors my site every evening and I'm usually only "caught in the loop" for a max of about 15 minutes each night.
Just would be nice if InfoPop would fix the software. There's obviously a problem if so many others are afflicted in the same way. So why not just fix it?