No need to change if you're able to do everything you wanna do without
effort. So long as MS Office 2003 is getting security updates there
shouldn't be an issue. If MS stops the security updating service for
this version, then you should consider moving to something that's
supported, to avoid security exploits that keep getting invented out on
the howling ether. If you need to open Docx diles, MS has an Office
Compatibility Pack for free download that might work for you. This
allows you to open Office 2007 and 2010 documents in office 2003 and
read them. You can edit them too but can only save in office 2003 or
earlier format from your suite, which is for the most part fine if you
don't need the new features, and the saved versions are perfectly
compatible with the newer software.
By all means if you have the space the time and the willingness to
learn, play with the other free open source office suites (Like IBM's
Lotus Symphony, or OpenOffice.org or its other knock-offs), they don't
require you to remove anything, you'll still have all the MS stuff
working too so you can use either. However in my experience, except for
the simplest documents, I've always had very poor document fidelity with
reproducing MS Office documents in O
rg suite. The only other reason
you might want O
rg's suite is if some kind sole sends you an odt
document or such that Office 2003 can't read. But in my experience most
ppl don't do that.