Depends on your riding style. If you commute and treat each traffic light as an F1 start the chain will be knackered in 10-15K miles. If you pull away like an old fart and never hammer the throttle, keep the chain properly lined and adjust when required it’ll probably last 40K miles. On my F700 I looked at it every 700-800 miles and adjusted it probably every 2,000 or so, but then I commute!