Wear and tear and time will eventually take a toll on your bike shifters. If your bike shifters are not properly working, there is no reason to throw them out and buy a new set, unless you want to of course. You could buy the parts you need for your broken bike shifters and fix them so they work like new again.
Perhaps you just invested in an old school mountain bike but it needs some work. With shifter parts from Niagara Cycle, you can fix the stock shifters that came with the bike. In fact, we carry so many bike parts, you can completely rebuild your old school bike project.