It's hard to tell how long, but if you're specific about the amount of time you need, say ask for a rescheduling for a month later in order to allow for the dr to respond to the SAR, then this might mean a sooner date than an open ended postponement - but it really depends on how far ahead they're booking the hearings. If you turn up at the hearing without medical evidence, then there is a far lesser chance of success. There is also the possibility of the hearing being adjourned so the judge can request the medical records themselves, which means a longer delay and more stress. In my experience, it is better to have a delay and go better prepared, than go ahead with an earlier date and fail due to no medical evidence to back up the appellant's evidence. But in the end, it's your friend's choice.