Andrew
It looks like it keeps the last two months of the driver's laptimes.
These can be exported it you login to the browser.
I wish I had known this at the start so I could keep a record of my laptime progress throughout the seasons.
I only have last 10 races, including my quick races, so only a few days of history :(
I really wish it was unlimited, I would be wiling to pay for it. I also wish I could see my Kers usage every lap.