Can I upgrade to a higher build later?

Yes, in or out of warranty. Moving up a Premium tier needs a slot open in that tier. While you are in warranty, 65% of what you paid comes off the build you move to. After your warranty ends, 40% comes off instead, but only if your build was blocked or detected. Advanced to Private inside warranty: 65% of $200 is $130 off, so you pay $170. If you already know you want a higher build, just buy it now.