While recently doing an under-hood check on my V70, I noticed that the ribs on my serp. belt were hard, glazed and badly cracked. It had been in there for 51,700 mi, about 6yrs-3mos. This was a Conti-Tech belt, not a cheap one. Pretty good considering the heat here in Central Tx is brutal. Still looked fine on top. Frankly, I'm amazed it's been that long since I changed it.
I pulled it off and gave the idler pulley a spin. zzzzzzzzzzt. Very dry, but was original. The tensioner pulley spun nicely but said tsst....tsst.....tsst.....tsst when I spun it. It was also original. Just finished replacing both of these and the belt.