Better organisation of reviews

[Karl]

@Douglas_Gregor

If you start lining up month-long reviews (+ expected re-reviews) for, say, the dependency chain of Swift Concurrency proposals you'll almost certainly push yourself past the next branch date.

Looking at the cutoff dates for the last few releases:

• 5.1: March 18, 2019
• 5.2: December 9, 2019/January 7, 2020 (8 months)
• 5.3: April 20, 2020 (4/5 months)
• 5.4: January 7, 2021 (8 months)

So we do tend to have quite a bit of time between releases. I think there is probably some leeway to extend reviews within that time (maybe extending all deadlines by 7 days - so 14 days for re-reviews, 21 days for longer reviews).

@Douglas_Gregor

And longer review periods makes for more overlapping reviews, which means more things to track at once. We trade one problem for another.

Perhaps, but with the schedule you posted (very informative BTW, thanks!), we're apparently looking at 5 concurrent reviews (!) come December 10. So shorter review periods do not seem to be leading to less overlapping reviews today, and the overall load is still very high.