Good call - will do that and thank you.The best way to decide if you want/need the maintenance plan is to give your dealership's service dept. a call and get quotes for each required maintenance interval. Add it up and see how much you'd save if you purchased the plan. With my vehicle, if I purchase the 20K plan ( I don't intend to keep it past that), I save $80. I would assume that there would be a savings at each service. In addition, the plan is transferable to the next owner; although I don't think it will affect a trade/resale value. Personally, I wouldn't buy it beyond the time from when you want to sell it-- it won't really be a selling point. Remember what you said, " I purchased both for my Audi and didn't end up using either and canceling it/getting a prorated refund back". That pretty much answers your question.
With respect to tire plan...unless you're planning on have several flats I don't see how it wouldn't be a waste of money. Personally, I haven't had a flat in over 15 or more years. But, if CA is as bad as you say, then it may be a good idea for you. Again, call service and get out-of-pocket quotes on tires/installation.