I first saw Jay when he was a guest on Letterman's show in 1983 (pretty sure it was Letterman). It was Christmas week and Leno mentioned that he was really stoked because his wife had gotten him a new clutch for his Ducati for Christmas. I became a big fan of Leno simply because he was cut from the same bolt of cloth that I was ..... I rode (and loved) motorcycles and loved cars. Jay was just a stand up at that point. I've been a big fan of his ever since.
The youngens here posting smack about old people will get a nice lesson one day soon ..... time zips by buddy and your time is just over the horizon

You are probably not old enough to recognize the cultural significance of the Tonight Show franchise. Having watched Steve Allen, Jack Parr and Johnny Carson create the most succesful francise in television history, I can appreciate it's heritage and can easily see why Jay fit the mold as well as he did.
I never liked Conan on Late Night and never watched him. His bits were just too juvenile for me. It wasn't that I didn't get it, it was just peepee caca humor reminding me much of grade school humor.
That being said, I decided to watch the Conan Tonight Show just out of curiosity. My impression was that he toned down the juvenile aspects and tried just a little to be more mainstream. I don't find any of his filler bits funny at all (Conando, Year 3000 etc). I was very surprised however to find that Conan has excellent interviewing skills, gets into a great rapor with his guests, gets the best anecdotes out of his guests and is truly a very innately funny guy. I love Andy's role in the sidekick spot and think they work great together. I grew to like him personally and watched him every night. I would probably watch him again where ever he winds up.
Now, that being said, I am still a Leno fan. Leno's car savy is second to none. He is sincere in his love of cars and technology and is much more knowlegeable than most people realize. I love "Headlines" and never missed a Monday night in 17 years (or so) as a result.
As for old people needing their sleep, Dude, are you ever naive

I'm in my 60's and never go to bed before 2am. I'm in my Playseat 4 to 6 hours a night, own every racing game made for PS systems and do more stuff than you'll ever imagine.