Hmm, I rely on myself and sometimes forums like this. I support my dealer in a lot of ways, but a profitable purchase for both of us does not obligate me to purchase everything from him for life.
My dealer and I have a great relationship that has continued after the sale, but he switched brands of chemicals he carries to a brand with better margins that I dont' think works as well. Should I stay with him? After a year or so, I think I can handle any water problems as well as he can.
While you may not always need your dealer for water chemistry issues. You probably need your dealer for your warrantee repairs.
Almost every brand of spa has an exclusion in thier warrantee against improper water chemistry.(read your fine print).
Most dealers will go ahead and fix your spa under warrantee even though they could easily prove that improper water chemistry had at least a small part in your spa failing. They are willing to do this because they want your business.
There is a chance that if you start taking your business elseware that your dealer will no longer fix problems caused by water chemistry under warrantee.(they do not have to). Instead they will charge you for the repairs. I used to work for a dealer that did just this. It is amazing how often dealers take you business personally.
While you are under no obligation to buy your chemicals from your spa dealer. I can assure you that your dealer would appreciate it if you did.
Keep in mind that your dealer is not under any obligation to bend the warrantee rules for you. Most will, but they do not have to.
F.Y.I. After only having one spa for one year it is very unlikely that you have came accross every water chemistry problem that can occur in you spa. Your dealers experience is MUCH more valuable than you realize.