Namespace declaration - good practise

Hello !

I have a lot of XSL that process many business documents. Each XSL 
declares at least 15 different business namespaces, excluding technical 
namespaces (http://www.w3.org/1999/XSL/Transform, 
http://www.w3.org/2001/XMLSchema and so on).

We have problems when creating a new XSL, in copy/paste namespace 
declarations, and refactoring (namespace modification) is almost impossible.

So, I'd like to declare namespaces strings as constants, and use these 
constants in XSL.

The only way I've found is to declare a DTD with entities, one entity 
per namespace :

<?xml version="1.0" encoding="UTF-8"?>
<!ENTITY nsXF "http://www.lefebvre-sarrut.eu/ns/xmlfirst">
<!ENTITY nsAdded "eu:lefebvre-sarrut:mcqueen:publication:added">
<!ENTITY nsXfPub "http://www.lefebvre-sarrut.eu/ns/xmlfirst/publication">
<!ENTITY nsEls "http://www.lefebvre-sarrut.eu/ns/els">

Then, use this DTD in my XSL :

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE xsl:stylesheet SYSTEM "../../namespaces.dtd">
<xsl:stylesheet
   xmlns:xf="&nsXF;"
   xmlns:added="&nsAdded;" ...>

Oxygen have a convinient completion on entities that simplifies declaration.

Am I the only guy to do this ?

Is it a good practise ?

Best regards,
Christophe