My suggested ranking system would fix this - although I was only meaning for it to apply to the daily games, not to all quizzes like the system you are asking about.
At the moment you simply get 10 points per correct answer and these accumulate over time. In general, the longer you have been playing quizzes ( assuming you play regularly ), the better your ranking. If you have a fairly high ranking it is unlikely it will change very much if you are absent for a short period of time. Even the top 100, 000 places or so has very little movement.