You could get that behaviour for a number of reasons, such as the"Allow only one copy of document in memory" setting, document timeout or pre-load options.
Also 10gb QVS would mean quite a large QVW document.
It also depends on which browser method the users are using, Ajax doesn’thave a 'close session' mechanism so the session remains open until the timeout is reached.
As a side note, there is a way to stop the users getting disconnected,called 'graceful document refresh' but I’m having trouble with this feature at present and QT are looking into it.