I am always having a concern about using the micropipette. however by time it will lose its accuracy.

so whatever the brand in use, do a calibration for it  by yourself. you just have to weight I mL drawn with your micropipette, it should be equal 1g for water.

Dear Aida, 

I know how to do calibration for different micropipette, but the question related to the price and the brand does it worth to purchase the expensive one, in a time that the cheap one should be calibrated over time ? 

As long as you verify its accuracy & precision, brand doesnt matter