XTOL in a replenished line will last a long time - if it uses nitrogen burst agitation. The nitrogen bubbling through the developer will carry away oxygen as well as prevent air from getting at the developer.

I had a batch of XTOL fail while clear a year ago. Probably 6 months old, stored in topped-up bottles. I had heard rumor that Kodak had somehow addressed the issue and so I bought a brand-new bag - same old stuff...