well.. i also had exactly the same question.
i asked that to a friend (who is doctor).
his answer was bascily this:
it wont kill you instantly, using lenses longer than you should but over the time
you wear them (for example 1 mounth), they get tiny tiny breaks, where bacteria
i also tryed using my lenses for 2 or 3 months... but then after some time my eyes began
to get a bit red and that was the point where I bought new ones. just try it and you will see m8 =)
I didnt want to buy new ones, because they were very expensive.. (for a pupil) but then i searched
for cheaper ones and found some.
now i pay only 1/4 of the old price. and they are also good