I bulk-bought chicken Oxo cubes last year as they were on a ridiculously cheap offer, the expiration date was Oct 2012. I've just opened the last box (good timing or what! ) but the cubes are squishy, not crumbly. They taste fine. It's odd, because the last box were all OK and they were the same date.
They always used to be squashy they have only become the weird solid cubes they are now in recent years.
Im pretty sure they have quite a long use by date - I was quite concerned when oxo released the bottles of stock that people would switch to them and they would phase out the cubes - I dare say the bottles have a much shorter life.