Toyota Repair: 98 Toyota Avalon, rear struts, time mechanic

Question
We inherited  '98 Avalon from my in-laws, now at 140K miles.  He replaced front strut tops in Oct 07 at 112K miles (at Toyota dealer).  Our mechanic (independent, not Toyotal dealer) says the car needs new front & rear struts.  Car drives smoothly with no noise.  How do we know if this repair is necessary?  Also, is it more cost effective to replace tires & struts at the same time?  Mechanic is also recommending tire replacement; tires were replaced Oct 07 at same time as front strut tops.

Answer
If the struts are not leaking and the car seems stable on the highway the struts probably don't need to be replaced, ask the mechanic for an explanation why he thinks they should be replaced. I have no idea if the tires need to be replaced without looking at them, if they are worn they should be replaced and also at the same time an alignment should be done.Maybe you can get another opinion on this but keep in mind most tire stores will always try to sell you more stuff than just tires, that's how they make their money.