By 'bottom out' I assume you hear a loud thump and feel a shock through the body and / or steering wheel? If so then good chance your struts are shot. They are generally only good for about 80,000 - 100,000 miles. However there are other things which could cause front end noises: failed thrust arm bushes, upper strut mounts, sway bar links, tie rod ends. If the front seems soft and sloppy on corners, or you can easily bounce the front up and down by pushing on a corner, then you should replace the struts.
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