If the Dataone is in constant use then it will not disconnect usually. This is how ALWAYS ON is supposed to function.But if you leave the connection on and switch OFF all browsers and also the Email client and also do not have the Keep ALive set for quick checks then also the ALWAYS ON is supposed to keep net connected but BSNL has done one thing for the benefit of the consumers that it has programmed the system at their own end such that the connection disconnects after 30 minutes so that the small usage of packets is also stopped. I think if you have the connection under continous use then it disconnects at 24 Hours use. Again its a security measure in case the net is being misused by an outsider. This 24 hour funda was observed by me 2-3 times in my connection when I checked usage at BSNL site. It was reading exactly 24:00:00.Otherwise the connection is very stable with BSNL.