I think belt replacement recommendation is upon inspection during oil change. Could anyone give an indication on when they replaced theirs or noticed signs of needing replacement? Mine is almost 10 years old with only 50k miles. Being old school, i usually replace the S-belt 7 years/120k miles during the same time as timing belts. Of course old school Toyota timing belts were made by Mitsuboshi while S-belts were made by Bando. I know the LS no longer has timing belts but old habits die hard.
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1. Belt - Bando brand (6PK2100)
2. OEM tensioner pulley i believe is made by Dayco (suggested by toyota to be replaced when the serpentine belt is replaced) (Most updated Toyota Part # 16620-0W131 / Dayco 89380)
3. No 1 Smooth Pulley: Replaced upon inspection (Likely Koyo) Toyota Part # 16603-38030
4. No 2 Grooved Pulley: Replaced upon inspection (Likely Koyo) Toyota Part # 16604-38020

 

My 12 yr old tensioner wheel disintegrated at 150k. So I would definitely check to see how it looks. Replacing just the belt was easy. Putting the tensioner in myself was a brief pain until I figured out the knack of putting it in. It would be easy the second time.

Although the way mine went out, I figure the bearing just failed one day, heated up and melted. The outside looked fine.
The Dayco tensioner was $85 and the Bando belt was $17 in 2019.

 

My belt looks in excellent shape. I occasionally spray it with aerospace 305. My car is in arid conditions and often under a car port away from the +100F sun.

All pulleys look in great shape and spins freely as well. I don’t pull off the belt often to check since I don’t want to break spring tension on the belt or tensioner.

I buy parts in advance depending on how good a sale is but not too far in advance to have new “old” stock.

Currently (Sept 2022), the bando belt is $12 from rockauto and dayco tensioner is $77. I would consider that normal price. Once in a while the Koyo No1 pulley would show up on rockauto or eBay.

I haven’t seen a tensioner pulley melt like that. I thought it would whine before it seizes but I guess it could seize immediately.

 

I would replace the belt anyway, it is just too old. If pulleys spin freely, have no play and do not have any kind of visual damage, I would not replace those.

 

That tensioner seemed to go south one day after I accelerated very fast into traffic. Maybe it was right on the edge and that pushed it over. I thankfully made it home before the car overheated too far. Lucky.