mmmmm, you bwill be kicked off regardless after 2 hours because it's simply too difficult (read expensive) for your ISP/BT to keep FRAICO connections open constantly, I use an ISDN router for my connection and it automatically reconnects after the two hour cutoff because the router handles it all, I have NO clue how the USB box handles it because it caused me no end of problems and I nuked it asap
However, whenever my router detects a request to the internet it auto dials, is there a setting in the USB ISDN box drivers? and my advise would be to either get an ISDN router or setup a linux fileserver box with a cheap ISDN card in, set up a network and the linux box can act as the router, whatever you do get rid of the USB connection