Decred has 28 days and here is another exchange offering staking without any lock up. They do disclose that there will be a withdrawal queue and you may have to wait to withdraw, so we will have to see how it works out, but I would be surprised if there were ever a long waiting period on the queue (if any at all), and certainly not 28 days.

https://www.kucoin.com/news/en-decred-soft-staking-official-rules