I would ride 10,000 miles

"Buy the best chain you can afford and then keep it clean and lubed. Put on a new chain at least once each season or when there is any measurable stretch. Determine stretch with a Rohloff Caliber 2 or Park CC-3 chain-wear indicator (available in many bike shops).

Some pro mechanics recommend chain replacement every 1,500 miles. I think you can go 3,000 miles easy if you use ProLink chain lube. The boys who make ProLink have had several test pilots out there to determine how long a chain will last with their product. At 10,000 miles, they say, the chains may fail from fatigue but still show almost no measurable stretch. That is amazing.

I still think, if for no other reason than guilt, you should replace your chain every 3,000 miles even if you use ProLink. Just keep track of the miles. If you use other chain lubes, the stretch test applies."