Just do a B service every 2 years, especially wanting to avoid having a caliper seizing up due to lack of maintenance. Worse case scenario, that happens and you'll have to spend more money on rotors, pads, caliper...as opposed to just having the brakes serviced. If dealership labour cost too much, you can always bring it to your local mechanic, but have them give you a copy of the invoice indicating what repair/service was done for future record. (Sometimes Subaru/Toyota Canada would like to see these documents in case of a warranty issue)
I like to do a B service myself after every Winter season just to be on the safe side. All the salt and snow that our cars go through on a yearly basis is just too much.
