I notice that it's only a 12" screen? Are you sure that's big enough??
Regarding when... well if you need it now get it now, otherwise I'd say wait until nearer the time. A similar machine will be be cheaper by then, or a better spec one will be available at the same price. That's the way it is!
But get it in good enought time to get used to it before you go!!
Also... GET A BACKUP EXTERNAL HARD DRIVE!!!
The last thing you want is your PC to be stolen. It happens all the time. The PC can be replaced, but the work you have on it can't!!