Hi Airmann,
I actually did some calculations and here is what I worked out. The closest any two airways are spaced in almost any part of the world is 10NM from centre line to centre line (am I right here? Or is it 20?). At a ground speed of approximately 500kts if one were to turn 45 degrees left or right one would have to cover approximately 14 NM in a straight line before intersecting the next airway and this works out to around 1 minute and 40 seconds. So if you were to descend at 6000fpm you would lose approximately 10000ft. The emergency descent would take no more than 5 seconds to initiate so that leaves you with 1 minute and 35 seconds to judge distances and decide where to navigate.
It is all very theoretical as airplanes may be flying directs to or be on specific heading/offset to avoid weather for example. As vilas stated before it is all a matter of situational awareness and being familiar with regional procedures in case of decompression for instance.
Always make sure that, according to the area that you are overflying, you know what the regional procedure states should you require an immediate descent without obtaining a prior ATC clearance which will be the case in a rapid decompression.