Session Files Question

Yes, the same garbage collector should kick in to remove old session data from the database.

But be aware if you setup a VPS on your own instead of using services from a webhosting company. Some linux distro's, like Debian for example, ship with the default settingession.gc_probability = 0. Wich mean that php will not run the garbage collection stuf. Debian's philosophy here comes from a security point of view that old sessions should be destroyed with a cronjob instead of by a php instance. Just some side info to keep in the back of your mind.