Suzuki say to change the semi-synthetic motorcycle spec 10w40 every 4000 miles and the filter every third time or so. We would change the filter every time. Take the right fairing lower off for ease of access.
Spark plug change
You’ll need to remove the seat pads, lift and support the tank and remove the airbox to get to the plugs (NGK CR9E or Denso UR27ESR-N). Also disconnect the cable block connectors to the stick coils before pulling them off the plugs..
Top end overhaul
Valve clearance adjustment is by shimunder-bucket so that means camshafts out if any have gone tight or loose. You’ll need to remove the injectors before the rocker cover can come off.
This would be a most-unusual occurrence. However the only special tools required are a clutch holder and flywheel puller.
Fork oil change
Take the legs out and give them a proper strip and clean when changing oil. Look out for corrosion on the stanchions but don’t worry too much if the nitriding is coming off; it’s only cosmetic.
Give the six-piston calipers a good clean and be ready to replace seals on a regular basis if the bike does a lot of wet weather and winter work. The piston bores were machined after the caliper halves were anodised so are prone to corrosion build-up behind the seals.