Shock Struts for Mazda 3

I have a 2006 Mazda 3 hatchback that has about 107K miles(mostly highway) on it. I am wondering about the timing that I should get the shock struts changed? It seems to be working fine, but is there something I should be noticing if they are not?

You will notice that the front end seems to float or keep bouncing after hitting a dip or bump in the road. The worse case comes when driving over a bridge.

The support structure of a bridge causes a small wave shape in the road surface. You won’t notice it in most vehicles, but when the shocks/struts go bad, the vehicle will begin to amplify the up and down motions caused by that wave shape.