N64 control sticks then to wears out really quickly after some use. The sticks become loose and you get white plastic dust around it. You can prevent this easily by applying some grease to some parts on the stick. I have been using this for at least 16 years and all my control sticks are still in fantastic condition. I typically get comments from people that can't believe my control sticks are still in an almost like new condition - this is the secret.

You need a grease made for plastic parts. I use grease made for the plastic gears in RC cars. First open up the control stick. You need to apply it to the indentations in the white cup and on the inside of the black gears and on the ball of the control stick at the bottom. There is a fantastic guide on how to apply it here with pictures: http://www.mmmonkey.co.uk/nintendo-64-control-pad-repair/

This is a picture of the stuff I have been using for a 16+ years: