The true of the upgrade"
If you upgrade in the 90-day from R7 to R8 without upgrade licence at the end of the 90 days your IPO it is going to BASIC MODE.
If you upgrade with upgrade licence, from any, you don't have any problem. Alway with upgrade licence from R6+.
Only if you have Essential, and put a upgrade licence to r8, all licence profile like power user, etc. etc. this license profile it's going to sleep until you buy a R8 preferred license.
That's all.
From R7 + Upgrade Licence = Cheaper
From R8 Directly = Expensive
Regards!
Djmtrar