1999 Honda Accord oil loss

i am losing approx a litre of oil every 500-700 miles of driving most of my driving is motorway and dual carriageway around the 70-80mph range i have looked around the engine and cannot see any oil leaks on the block and there is no oil left when the car is moved also i have checked the exhaust for blueish smoke and non is apparent, i have been told it could possibly be the valve stem seals. is it worth going straight for this or is there any other courses of action i could take