IIRC on the Standard Banc website it askes you if you want to continue (not sure if it was SB or ABSA online banking) Can't there be a funtion like that? 15 min is real short. (I know it is for security, but still)
This has been mentioned before and I think they are changing it to have that ability, but I am not entirely sure. You can download and use this browser http://www.myRefresher.com it has a setting that automatically refresh so you don't have to log in again etc.