2004 Tacoma DC with 109k miles, new leafs and coils?

I have a 2004 Tacoma DC with 109k miles. Prerunner. How does one know when they need new leafs and coils? If I got them prior to needing them would thei improve the ride much? I am mostly interested in highway driving (to surf) and smooth ride is paramount. Will probably do new Bilstein's in next two weeks, any thoughts are welcome.

No towing, no heavy cargo, no heavy offroading.

 

If you ride rough, want a lift, or unhappy with your performance in suspension. Also if you do highway i would look into OME dakars + 881's, and nitro shocks.

 

thanks for the tip, noted!