MacBook – My MacBook Pro Mid 2012 screen is black and then just vertical stripes (like a glitch). Why and how to solve this

A long uptime is four days? My MBP has uptimes of weeks. Not as snappy? I guess you're running out of memory or something else is wrong.

I've never had this issue where the machine is not as responsive after closing the lid as opposed to rebooting. I generally only reboot because of WiFi connection problems or software updates.

To answer your question - just close the lid. Only reboot when necessary. When closing the lid it goes into a sleep state which I think is very nice because when you open the lid it is almost instantly awake and ready to be used. While if you power it off it will take some moments to be booted.

You could leave the lid open as well if you like. The fist thing that is probably is gonna fail is the battery. To keep that in good condition make sure you keep your battery charged (there are other topics about this how to do this and what is the best).

In the end, the machine is built to be used and you should just enjoy using it without thinking to much about what is best. Apple already has that done for you :).

It sounds like your backlight has broken. The LCD screen needs to be lit from behind before the screen contents are more than vaguely visible. If you boot the machine again, and shine a bright torch from the front, you should be able to see your usual screen layout for login etc, but obviously everything is going to be very very dull. If this is the case, then you can get that fixed with relative ease at various repair centres or through a slew of online guides.

Sometimes on older hardware it's not the backlight that's gone, but instead the tiny starter/transformer that is required to kick a backlight into life, although this type of method isn't used on modern LED backlit screens like your Macbook