Overhaul is not a maintenance thing....its a repair thing...no real need to overhaul unless ur bike is super high mileage n u may need to hone the cylinder walls, only if the condition is bad. Otherwise, overhauling is mainly to tear the engine apart n replace a broken or worn part.

Age by years doesnt determine the need to do this n that...except maybe for the fluids n some plastic parts that might deteriorate... Mileage is what mainly determines the need to do something.

Can just follow ur manual by mileage n u should be fine unless ur bike.

Depending on mileage, id do a valve clearance check or some mechs refer to as grind valve.

my bike 63k... i just changed my oil n oil filter only... air filter washable, already washed at 40k km when i did my valve clearance. planning to wash at 70k km.

valve clearance basically ensures clearance between ur valves n pistons so they dont bang each other.

if u havent done valve checks... go do it... other than that, just service like normal