We never put all our eggs in one basket. Usually when we get where a higher percentage of our purchases are coming from one particular supplier, they do something stupid and tick us off and we drop them or start moving more of our business to another supplier. We actually found a few good places locally to go to after we looked pretty hard. You just have to make it a continuous thing you do to keep watching for good deals on things you use and pick-up a bunch when you see a good price.
Our company has developed a real love for Landa Hot Water units and Water Jet surface cleaners, but that's about it when it comes to any loyalty to particular companies or suppliers.