Its not so bad idea to cheack immediatelly Your valve clearances and change belts, but if nothing serious cant be found, then i would say, that valves should be checked every 20 000kms(10 000km, what manual says is little too often). Belts change every 20 000kms or every 3 year(as manuals mentioned every 2. year is too often).
Fuel system needs attention: fuel filter change every 20 000kms !!! You should make big adjusting/maintain with TPS set, Syncronization, injector maintaining(need special store and tools), idle adjustment, etc IF such have never done to Your bike !!! One advice: change fuel filter from inside tank to outside, so its much easier to change, when needeed.... Put only suitable pipe inside tank to filters old place...
I have had only good result with Champion spark plugs and only bad from NGK.....
About valve adjustment: Do You know, what and how to do it? if no, then there are in internet many sites, where U can find how to do Ducati valve check. Its shown in newer ST workshop manuals also.
Do U know, how TIGHT/LOOSE those belts have to be? Its not only, are they looking good or bad...... Also about this thing You can find very good advices from internet and using 5mm and 6mm allen tools for "testing" is very used method and very(enough) accurate.... and simple!
