I received it earlier today, but neglected to read the fine print until I saw it in your post. Not only are you limited to one redemption (250 miles), but it is only valid for 7 days. My next flight is in 8 days.
I wonder what was the motivation to send this offer? I've used OLCI in the past, so it's not as if they're encouraging travelers to go online instead of clogging up queues at the airport.