I think the reason some people are concerned that clones will eventually "lose something", or deteriorate over time, is because of the way they percieve clones in the first place. As stated above, clones are thought of as "an EXACT replica", or in other cases the cloning process is thought of in terms of generations. It's not about replicas or generations.
It's the same damn plant! It is literally a cutting of the same plant. There is no replicating or generating involved. We've all heard of a lizard growing a new tail - well it's kind of like that, only, in reverse. It's like a lizard's tail growing a new lizard (sort of) - just a whole lot less complicated! IT'S THE SAME DAMN PLANT!