Missing Salah For A Long Time Due To Illness
It is eventually upto the person to decide. Few days which can be counted on fingers can be fulfilled by offering the remaining prayers. If days are too many, then it goes beyond the capacity of the person to complete remaining prayers through mere counting, in that case, approaches mentioned above can be adopted ( preferably the one which involves extra care ). There is some guidance available in case of Prayers left during menstruation cycles of women, where they are not asked to complete their leftover prayers after their periods. But since it is not something which repeats everymonth (coma) like periods, therefore, one needs to deal with this scenario with more care.