My best advice, put just a small pinch of kosher salt in the carafe before brewing. It will help tamp down some of the bitterness, if you don't like that
I am at the point where I no longer answer my phone if it isn't one of my contacts. If it is important, they will leave a message. I just press the hang up button on my watch immediately, if it shows an unrecognized number, local or not.
I think any age you are comfortable with. My son's school just started using Khan Academy as a supplement. He is in second grade, but third grade math. He really enjoys it, as do I.
The halo effect took a lot longer to go away for me then a few months, but it eventually did go away. Same with the dry eyes, it took maybe a year for me to get over the dry eyes. I am going on 10 years now and I have no lasting side effects, and I would no doubt do it again.