Over the holidays I acquired my first tube amplifier, a VOX VT20X. I'm not really sure whats required to keep a tube amp sounding its best for as long as possible or if they even require special treatment. what do you suggest I do for keeping it in optimal condition? Are there any circumstances or situations I should be wary of?
There's no special treatment, just avoid mechanical shock (tubes have parts that can move under shock, and they're obviously in a glass envelope), and moisture (including beer ...), the latter of course being true for any electronic equipment. And, as a rule of thumb, never leave your tube amp anywhere where you wouldn't want to sleep, e.g., in a trunk of a car parked in the cold etc. Tubes are also especially vulnerable when they're hot, so don't move your amp too much before it has had a chance to cool down.
But in general, tube amps are more resilient than many people think. Don't worry too much, just use common sense and the above tips.
There's no need to change the tubes as long as you don't notice any strange noises, and as long as you're happy with how it sounds. You would normally change the power amp tubes much more often than the preamp tubes, because they get to do all the work. Don't forget to have your amp re-biased after changing the power amp tubes. But it may take years before you might need to change them for the first time. On average, the more often you use the amp, and the louder you play, the sooner you'll need to replace the power amp tubes.
EDIT: re-reading the question I noticed that the amp model you got is a Vox VT20X, which is actually not a conventional tube amp, but a modeling amp with only one single 12AX7 preamp tube, and no power amp tubes. Everything mentioned above remains valid, but you won't need to worry about biasing and everything else related to power amp tubes. Furthermore, chances are that throughout the whole lifetime of the amp you won't need to worry about replacing that one preamp tube.