While spot buying can often work in your favor by allowing you to pick up cheap loads of product as they come available, in the long run, without a fixed price contract for necessary constant items, you will find yourself at the mercy of the market and of supply and demand.
With a fixed price contract you can forecast and prepare for future needs ensuring a steady supply of lumber or panel products at your negotiated price. The term of your contract and the price of the contracted product will generally be governed by industry standards (i.e. Random Length or Crow’s).
Spot pricing is, by its very nature, unpredictable and unreliable. Relying on spot buying can leave you short of needed product or necessitate purchasing at higher than average prices due to market fluctuations.
In order to buy well, one should always have product contracts to cover steady needed items and use spot buying for those special deals that come along.