The outline for my first game took quite a while to get right, several months I believe and 6 lots of revisions. Nowadays there are design guidelines available - if I was doing it fresh today, I’d have more information available for making my first outline draft closer to ready. The most recent outlines I’ve done have only needed a couple of rounds of revisions and weren’t at all arduous. In my most recent experiences, I was compensated for the outline independently of the compensation for the acceptance; if it hadn’t been greenlit I would still have got a fee for the work on the outline. I don’t know if this applies to every situation.
I agree with @Eiwynn’s comment above though that your best bet is contacting the staff directly as they’ll have the most up to date information about the process!