IMHO, chains don't "stretch". Chains either wear externally or internally. What is referred to as "initial stretch" is merely the internal lubricant being forced to the forward side of each roller under load. Once it's there, the chain needs a minor adjustment and you should be good to go. If the chain is cleaned and lubed on a regular basis it should last for lots of miles. Eventually the seals will wear out and the internal lube will get contaminated or lost and the internal wear will accellerate rather quickly.
So if you need to adjust your chain a lot, you probably need a new one.
