[ddouglass]

Update and Upgrade are not used that way by MTU, but as interchangable. If you want an answer to your question then I would suggest you submit a Support Ticket to Sales expressing your concerns. MTU is the ones who would have to answer this question.
As it stands right now you have 12 months from your last paid update to get further releases free regardless of what is contained in them. If you purchased 4.20 that would have been in June of this year and you would be able to update for free until June 2011. Obviously then that was not the date of your last purchased update if you cannot get the updates free at this point in time.