Thankfully, it doesn't sound like you'll have to deal with watching the kind of lengthy commercials you're used to seeing on TV. According to a Google Help page, the max video length for non-skippable ads is 15 to 20 seconds. That's still three to four times the wait if you're used to clicking the "Skip Ad" button as soon as the skippable format's 5-second countdown is done, but it's probably not a length that would deter you from watching something you really want to watch. It could still hurt creators who don't have a lot of loyal fans and whose content and niche of choice aren't that intriguing or unique, though.

When a creator gets access to the feature, it'll be auto-activated for all their previous uploads. They'll also be given access to tools that can track their non-skippable ads' performance. If they notice a decline in viewership or earnings, they can always deactivate it for all their videos in settings.