I often put YouTube on a continual music playlist, with video displayed when eating and just hearing the sound when doing something else.
From time to time, there is an advertisement, which can be for 5 seconds unskippable, 15 seconds unskippable, or longer, skippable after 5 seconds.
Sometimes these advertisements are quite interesting and I watch all the way through, if they are short I just let them roll through anyway. Recently, with music in the background, an advertisement started and after a while I realised that there was a man talking, no music: so I put YouTube as the displaying window and found that the advertisement had being going for about 5 minutes and was over an hour in length!
Recently there is one that arises that is about 5 minutes about a system for teaching.
One advertisement came on recently and it was a lady singing with a small group of musicians. I wondered what it was advertising. It was about three minutes long. It turned out that the group was advertising itself as a musical group.
I had not known of a musical group advertise itself like that before, well done them.