I regularly watch YouTube (I'm 27). I usually watch videos about woodworking, blacksmithing, machining, engineering, astronomy, math, chemistry, farming, and off-the-grid living. I find all of those valuable in that I learn something new nearly every time I watch one of those videos. That said, I also watch video game montages when I want a good laugh and some mindless entertainment.
Here are some of my favorite channels that I find watching almost always a good use of my time:
I cannot recommend Matthias' channel enough! He is absolutely amazing. I love the organic points in his videos where he messes something up and then fixes it and concludes "good enough". A true demonstration of the hacker mindset!
I believe he was a computer programmer full time before his YT channel and website took off. Watching him work makes me want to become a woodworker. Maybe someday I'll have the appropriate space and give it a shot!
I've recently started watching woodworking videos on YouTube. I read somewhere that Matthias was one of the early employees of RIM (Blackberry) and as it turns out, he has a bunch of those patents in his name: https://www.google.com/search?tbo=p&tbm=pts&hl=en&q=ininvent....
Here are some of my favorite channels that I find watching almost always a good use of my time:
Engineering Practical Engineering: https://www.youtube.com/channel/UCMOqf8ab-42UUQIdVoKwjlQ
Physics Sixty Symbols: https://www.youtube.com/channel/UCvBqzzvUBLCs8Y7Axb-jZew
Woodworking Matthias Wandel: https://www.youtube.com/channel/UCckETVOT59aYw80B36aP9vw Frank Howarth: https://www.youtube.com/channel/UC3_VCOJMaivgcGqPCTePLBA
Astronomy DeepSkyVideos: https://www.youtube.com/channel/UCo-3ThNQmPmQSQL_L6Lx1_w
Chemistry Periodic Video: https://www.youtube.com/channel/UCtESv1e7ntJaLJYKIO1FoYw
Blacksmithing/Machining Clickspring: https://www.youtube.com/channel/UCworsKCR-Sx6R6-BnIjS2MA Alec Steele: https://www.youtube.com/user/alectheblacksmith Brian Oltrogge: https://www.youtube.com/channel/UCOywIdppbhn6hkgcEtDMatg
General Interest Science Veritasium: https://www.youtube.com/channel/UCHnyfMqiRRG1u-2MsSQLbXA Vsauce: https://www.youtube.com/channel/UC6nSFpj9HTCZ5t-N3Rm3-HA Smarter Everyday: https://www.youtube.com/channel/UC6107grRI4m0o2-emgoDnAA Tom Scott: https://www.youtube.com/channel/UCBa659QWEk1AI4Tg--mrJ2A
Cooking Chef John: https://www.youtube.com/channel/UCRIZtPl9nb9RiXc9btSTQNw Andrew Rea: https://www.youtube.com/channel/UCJHA_jMfCvEnv-3kRjTCQXw Byron Talbott: https://www.youtube.com/user/ByronTalbott