Is A 2012 Mac Too Old For High Sierra

MacOS High Sierra may not offer many radical changes to the user experience, but there are plenty of quality of life changes, and its under-the-hood alterations should help future-proof your Mac.
I have a 2015 Macbook Air 11' running Yosemite. Because of unstable Internet at home, I have not tried to update to a more recent version of the OS. How to download adobe photoshop for free for imac os x 10.8.5. I have now discovered the joy of free Internet at coffee shops and libraries.
So, my questions are should I update? What issues might I encounter? For example, 1. Will I have to spend the night at the coffee shop to install it.
I understand it can take a long time. Is there a way to save my current operating system on my 3Tb external drive using Time Machine, so that I can reinstall it if I have issues with the installation? Or do I need some other kind of software and if so what would you recommend? All advice gratefully received. Thank you, Carole. First of all, you should be making regular backups (with Time Machine or another archiving utility) on a regular basis, regardless whether or not you will be imminently upgrading your computer's operating system.
Here's how I would do this. Acquire an external USB drive that is the same size or a little larger than your Mac's drive. Use Carbon Copy Cloner and clone your Mac's drive running Yosemite. Boot from the external USB drive to verify that the copy is functional. Download the macOS High Sierra Installer from the Mac App Store at whatever location has decent Internet, but do not run the installer. Just leave it in the Applications folder and go home. Acquire an 8GB USB thumb drive or an 8GB SD card and appropriate card reader.
Use your favorite search engine to look for 'mac OS High Sierra bootable USB.' There will be a number of online articles that explain how to create and use a bootable USB thumb drive with the High Sierra installation instructions. Follow those instructions. I have two Macs, so it is handy to have the bootable USB installer thumb drive. I download the macOS Installer once, install on each system. The next time around, just repeat.

Clone current drive to external USB drive, download new macOS installer from Mac App Store, create new bootable USB installer, upgrade software. I've been doing this for years. First of all, you should be making regular backups (with Time Machine or another archiving utility) on a regular basis, regardless whether or not you will be imminently upgrading your computer's operating system. Here's how I would do this.
Acquire an external USB drive that is the same size or a little larger than your Mac's drive. Use Carbon Copy Cloner and clone your Mac's drive running Yosemite. Boot from the external USB drive to verify that the copy is functional. Download the macOS High Sierra Installer from the Mac App Store at whatever location has decent Internet, but do not run the installer. Just leave it in the Applications folder and go home.
Acquire an 8GB USB thumb drive or an 8GB SD card and appropriate card reader. Use your favorite search engine to look for 'mac OS High Sierra bootable USB.' There will be a number of online articles that explain how to create and use a bootable USB thumb drive with the High Sierra installation instructions. Follow those instructions. I have two Macs, so it is handy to have the bootable USB installer thumb drive. I download the macOS Installer once, install on each system.
The next time around, just repeat. Clone current drive to external USB drive, download new macOS installer from Mac App Store, create new bootable USB installer, upgrade software. I've been doing this for years. Click to expand. Thanks for the detailed reply. I do make regular backups to my usb hard-drive, which is 3TB.
My laptop has 256 GB storage. So do I put Yosemite on that drive or do I need a thumb drive? I don't think I have ever seen a thumb drive with more than 256 GB storage. Or am I misunderstanding your instruction? In a coffee shop today I did download the MacSierra installer. It is in my application folder, but it is only 19.7 MB. Is that right?
It downloaded very fast. I didn't click on install -- too chicken. My laptop is my only computer. So if I screw this up, I have nothing, except my iPhone SE and original iPad Air. There is an alternate approach to this, if you're making Time Machine backups.
Time Machine allows you to roll-back to a previous period in time (such as just before you upgraded the OS), restoring the entire computer to the state it was at that moment. To do such a roll-back, you'd boot the Mac into the Recovery system > Restore from Time Machine backup. You'd then be able to pick the date/time you want to restore to, and just walk away until the restore is done.