If all your coins are on one address it will take time for the coins to separate into smaller batches and staking will become more and more frequent as that continues to take place. To speed up that process you can divide the coins yourself to multiple address's with the coin control feature. I think that block times are pretty stable at roughly 150~ blocks a day. Both exchanges do not stake so anyone who has sent coins to exchanges or rather any coins sitting on exchanges will cause staking to slow slightly for a short term. I hope that answers your questions, thanks.