Re: Serious Illness
Rules of thumb in this situiation are not terribly useful. Two years' income might be sufficient for you but completely inadequate for me, or vice versa.
A better approach is to sit down, make a list of your various commitments, and then work out how you would manage them if you were unable to work. A good start is to have all loans cleared in the event of a serious illness.
Have you looked into Income Protection, which can pay a valid claim and thus continue paying you an income right up to retirement age?