Just wonder how long does the effectiveness of the brake paste lasts?

Initially, my brake squeked frequently, when I brake from a slow speed. After applying the brake pad paste ( cost a bomb in Malaysia US2.65 per paste, if compare to partshop price of US$0.70 ) it worked for about a month or so. Now, the squeking sound is back.

My brake pad is original MB, by Textar.

Any further recomendations?

Thanks