It depends on the site. If there are a lot of users and you need to deploy an update during the middle of the day, even a little downtime could be disruptive.

It depends on the site. If there are a lot of users and you need to deploy an update during the middle of the day, even a little downtime could be disruptive. If you have a global audience then maybe there's no safe "after hours" time to deploy. Zero downtime deployments are fairly critical for a lot of Continuous Delivery / Deployment workflow, so more solutions the merrier as far as I'm concerned.