Well if they don't notice anything needing replacement when they do the ball joints even though the struts/shocks may not feel bad if you are going to keep it a long time they will need them sooner or later and like tvpierce said why not do a good thing that you will enjoy and not someone else. They will have the fronts half way off when they do the balljoints anyway.

You know like driving aroud with an old pitted windshield and then replacing it to sell it, and realising you should have done that for your enjoyment. hehe