The Voyager underwent a major refurb in 2004, after being launched in 1999. All ships get a freshening up periodically - maybe just a week long or so. I don't know when that last happened for Voyager but feel safe in saying it has. There was a rumor that the ship would undergo another major refurb last year but that didn't happen. I'd say it is ready for a good 3-4 week overhaul.