Or one update per calendar year?
maybe, but as I've heard some say, you are only allowed to get one each one year from your anniversary/purchase date. for me that is June 20, 2018, and I have received 3 within the first 10 months of ownership. I got 2 in 2018.
and it doesn't matter if they "revise" it at this point, the warranty book I have says Map Care: 3 years FREE map updates
not free once a year for 3 years, or whatever.
If they revise(d) it after my purchase, that's fine, it would apply to those that purchased after the revision, those of us that purchrased with the old wording are 'legally' are entitled to 3 years FREE map updates regardless of how many a year come out from the way it was originally written, and I suspect it would hold up in court as well if it was challenged.
"3 years FREE map updates" is not the same as "free once a year for 3 years", or "one free update per calendar year".
personally I have challenged manufacturers twice on warranty wording and won, both times in arbitration, they need to be specific in the wording not ambiguous, and if it is ambiguous then the arbitrator and/or court will find in favor of the customer, not the manufacturer.
I even challenged a former employer on their ambiguous non-disclosure and no right to sue for unpaid wages document and won, forcing them to back pay me over 10 years of overtime..