What is the optimal size of a block to staking in 9 days?
completely depends on if diff keeps rising. I would be surprised if anyone is consistently staking anywhere close to 9 days. I have a range of blocks between 5k and 10k and the average stake time seems to be around 15-17days. There is the odd one that gets lucky and stakes around 10 days and a few that are just stuck like a block of 12k at 30+ days.