Use a high grade stain and it will last for years. You will need to spend at least $30-40 a gallon for good stain. I use three different kinds depends on how much the customers wants to spend from $10 to $65 a gallon. The higher the oil content the better the stain and price.
Gary is exactly right: using just oil misses the UV inhibitors, stabilizers, pigment (if desired) and other additives which make a good stain, well, a good stain. Most stains are based on oil - it's the additives that make them work better.
I have used 'SuperDeck' since back when it was called "DuckBack" with great results.
