DOCBOOK-APPS: stylesheets availability

Hi,

I was packaging stylesheets-1.59 and came through various problems
because I tried to make it live along with 1.57, and not replace it.
But is that really necessary?
Do users really need the various versions of the stylesheets available
simply by not removing the old one, or does the difference between
stylesheets make this useless?

In other words: does a stylesheet version means a different package as a
new DTD do, or simply improvements?

thanks for your opinion, Camille.