Your drive belts, aka "fan belts", require minimal routine service but you should inspect them several times a year. Having one break on the road will really ruin your day.
When inspecting them you'll be looking for splits, cracks, frayed edges and delamination of the layers. If you see any of these signs, replace the belt - or, better yet, replace all of them and get a fresh start.
If they pass muster upon your inspection then check them for correct tension. Locate the middle of the span of each belt and press downwards. If you can depress the belt more than about 1/2" then the belts could use some snugging up. With Jaguar's clever threaded-rod adjusters this task is simplicity itself. Simply loose the nuts on each rod and you can adjust outward with ease to achieve correct tension. Do not overtighten the belts as the extra tension has been known to cause bearing failure on the belt-driven components.
Replacing belts is a bit more involved - a stinker of a job, really - primarily because they have to be looped around the cooling fan. Save yourself some aggravation and just remove the fan, you'll be glad you did. An extra half hour spent doing this really reduces the aggravation of the job. As mentioned earlier, it's best to replace all the belts at once and be done with it. Save the old ones as spares.
But, back to actually replacing the belts. Loosen all of the adjusters and roll the components towards the motor and lift the belts off. Take a minute to spin each of the now beltless pullies, listening and feeling for the noise and roughness of a worn bearing and observe the straightness of the pullies as well. You may discover the source of a mystery noise! Install the new belts making sure that you loop them arounf the proper pullies. Snug up the adjusters, reinstall the fan, and that's it. In about a week go back and snug up the tension again. New belts usually stretch a bit.
Unless inspection reveals a problem earlier, plan on replacing the belts every 30,000 miles.