They can use a bit of oil now and then.
Mine uses none on general day to day riding, but if I go play in the alps with lots of high revs and serious engine braking, it'll use a litre of oil in a 1000 miles
(also an 03 ST4S)
I usually check it when returning from a ride. Slap it on the centre stand on level ground and check it about 10 minutes after you've stopped.