Brake pads are a wear item so you should expect to replace them on a regular basis. If you have been riding regularly then 1.5 years is a pretty long life for a pad. Koolstops pads seem to be one of the best and may improve your stopping but don't expect them to last any longer.
pads also come in different compounds of rubber. The softer rubber gives more braking performance in wet conditions but does not last as long. Harder rubber lasts longer. Some fancy pads have more than one type on the same pad. kool stops are good. Avids and shimano's higher end xt and xtr pads are top notch. Several offer a cartridge style system where once installed you only replace the rubber not the shoes. Personally I like the Avid pads.
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