Just wondering, if something is re-released/re-issued does the copyright have to be updated the the year it was re-released? 

An updated version is considered a derivative work; the copyright on it only extends to whatever new material is added. The material in the original work is still under the original copyright; its copyright date does not change. If something is just re-released without changes, the copyright does not change at all (as there's no new creative material to copyright); only if it was changed is there any new copyright, and that is only on the new material (e.g. a new edition of Frankenstein might have a foreword, which would be copyright from when it was first published, but the basic text of Frankenstein is still public domain).

If the work is in fact a derivative, a copyright notice should have the year the derivative was first published, but it's only a derivative if it was changed.

An updated version is considered a derivative work; the copyright on it only extends to whatever new material is added. The material in the original work is still under the original copyright; its copyright date does not change. If something is just re-released without changes, the copyright does not change at all (as there's no new creative material to copyright); only if it was changed is there any new copyright, and that is only on the new material (e.g. a new edition of Frankenstein might have a foreword, which would be copyright from when it was first published, but the basic text of Frankenstein is still public domain).

If the work is in fact a derivative, a copyright notice should have the year the derivative was first published, but it's only a derivative if it was changed.

What about re-masters?

From what I can tell through Google (NB: I am not any form of lawyer, this is not legal advice), it's something of an open question when a re-master is a derivative work. Record labels are trying to claim that it is, because starting in 2013 musicians became able to revoke copyright transfers made starting in 1978 (the rule is 35 years after, for a copyright on a sound recording made after 1978), which would normally mean the record label would not be allowed to sell the sound recording anymore. If the record label makes a derivative work before the author terminates the transfer, they can keep a copyright on the derivative work even if the author revokes the transfer (the label would have no control over the original recording and couldn't stop the author from doing what they please with it, but would have control over the derivative work). So, labels want a remastered work to count as a derivative, because they often remastered it anyway for a digital version and want to keep selling the remaster. Artists want it to not count, because that would mean they could keep the label from selling the remastered version (so only the author's version would be on the market).

From what I can tell, remixes have often been considered derivative works; remasters have not generally been, but there is some argument they could be under some conditions. It really depends on specifics; you'd have to talk to a lawyer for the specifics of your case.