My 1993 850 has 56000 miles and it does not yet appear that it needs new front brake pads. Should they be replaced anyway because they are ten years old?
If they should be replaced, is there a Volvo specific kind of silicon grease that should be used for the slide pins and back plates or may a generic silicon grease be used?

"Should they be replaced anyway because they are ten years old?"

No. Base your decision for replacement on the thickness of remaining pad material or a need to correct a shortcoming in braking performance.

Or maybe you just have too darned much money, and want to spend it on something. :)

"Is there a Volvo specific kind of silicon grease that should be used for the slide pins and back plates or may a generic silicon grease be used?"

I used generic stuff on the slide pins, and have had good results with Permatex Disc Brake Quiet on the backing plates. That Permatex product is available from most auto parts stores.

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Jim Rothe, '99 S70 T5M,
http://www.jimrothe.com/volvo/index.html