How often do you restart your personal machine?

Maybe 5 or 6 times a year for my primary laptop.

So it's an old MacBook Pro, and it gets security patches that require a reboot sometimes. I'll usually defer them for a few weeks until I'm in a state where I'm ok to shut everything down.

Other machines, mostly Linux stuff, gets rebooted mostly by accident (ie. power outage). If there's a security patch that requires a reboot, I'm get around to that after a few months. I'd guess most things get rebooted about once a year.

Everything is set to go into sleep / low power mode as much as possible. But I don't like software which isn't capable of running indefinitely.

That depends. My Windows machine gets rebooted about once a week, by Microsoft, not by me. Microsoft doesn't value my work.

My Linux machine has been up and running since April 2014.

When I stop using it, I turn it off. And I need to use it, I turn it on. It's a desktop computer and since it boots in ~1 minute, there is no need for it to be on unless I have something explicit to do on it.

Probably once a week on average. Mostly just because I still believe it's good for the machine, not really sure about the science behind that though. 2015 MacBook Pro if it matters.

MacBook Pro 15". Probably once every three weeks.