<grin> Yup. I agree with you that you were being mean. So here's a few things to think about:
If there's "no good reason" to be up late... is there a good reason to be up early?
Why does a person need a "good" reason to be up late OR up early? If someone told you you weren't allowed out of bed until 2pm (because you weren't working the next day so you have no good reason to get up early), you'd look at them like they were nuts.
Think for a minute WHY you yourself WANT to be up early. A job to go to, sunshine to enjoy, etc. Each and every single reason you list out for being up early is ALSO a reason for being up late.
Same token, each and every single argument you would present to someone about WHY you don't want to stay in bed until 2, are the same arguments that someone would present about why they don't want to be in bed by 11 (can't sleep, have things to do, etc.)
I mean... if your kids were little, sure. Assign a bedtime. But your eldest is an adult... I'd already served my time in the USMC by the time I was 20 (signed up at graduation when I was 17), and your youngest is almost an adult. "Mommy says to go to bed" works with little kids, and is necessary for little kids... but if your adult child and older teenager are being respectful of other people's sleep, why would you try to control their sleep? If they have chores to do, they can do them at any point when the are awake. Even if they slept until 7pm that's still early enough to mow the lawn, vacuum, and do other "loud" chores.
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Now, if they were being DISrespectful of other's sleep (waking people, that is) that would be a problem to deal with, but by a "quiet after x time", not a "bedtime".
Just my .02