IF/When you do have a download, be sure to copy it to AT LEAST one external device -you should ALWAYS keep a copy (or two!) on an external device -since Adobe DOES SOMETIMES REMOVE OLD VERSIONS FROM THE SERVER -a usb flash drive or external hard drive, or write to a CD or DVD -plus a text file containing your serial number if you have a serial number program
@niallh94204942, because lr 6 is 64 bit there's an outside chance that you can migrate it from your older computer to your new one. i'm not sure you'd want to try that because it might not work and it might cause problems on your new computer.
but if you are comfortable with apple's computer restore, that's something to consider.