LOL! I'm hardly a full-fledged trademark expert, just a layman with a perhaps irrational interest in the subject. My early December 2014
Kaizen Factor piece on Lexus' LC 500 and LC 500h trademark filing (
http://kaizen-factor.com/lexus-registers-lc-500-lc-500h-trademarks/ ) did cite a couple of outside sources that addressed the time-limit questions you're asking about. Stephen Edelman of
Motor Authority, in his piece on Ford's refiling of the Mach 1 trademark (
http://www.motorauthority.com/news/1087911_mach-1-trademarked-again--possibly-for-2015-ford-mustang ) notes that trademark applicants are typically allowed six extensions lasting six months each before actually putting a product with the trademarked name on sale. Once the product goes on sale, however, the trademark can be extended indefinitely or until allowed to lapse by the original holder. Greg Migliore of
Autoblog wrote an excellent piece on trademark rules and cars (
http://www.autoblog.com/2014/08/07/trademark-next-iconic-car-name-feature/ ) that cites the example of General Motors' Buick Electra trademark. Although last used on a production car in 1990, the carmaker kept it alive for 24 more years, until finally abandoning it on July 28, 2014.
In the GLC and Encore examples you mention, I'm guessing that Mazda and American Motors/Renault abandoned the trademarks, allowing Mercedes-Benz and GM's Buick division to pick them up. GT is seemingly too generic to be trademarkable, and European trademark authorities feel the same way about GTI (which Peugeot and Suzuki used in addition to Volkswagen). VW was able to convince American trademark authorities to grant them sole use of GTI, however, and Suzuki had to rename its Swift GTi hot hatch Swift GT in the U.S.
I know I'm going in an off-topic tangent here, but I find the history of the Montego model name particularly interesting. This was first used by Ford's Mercury division in the 1968 model year for its so-called intermediate model line, essentially a gussied-up Ford Torino. Mercury continued using it until the end of the 1976 model year, when an expanded Cougar lineup took its place. During the 1980s, British Leyland's Austin marque, like Mercury, became enamored of model names starting with the letter "M" and Montego in particular. Although I haven't found an internet source to back it up, I recall reading in a
Car magazine of the day that BL paid Ford something like $1600 or $1900 (or, perhaps it was 1600 or 1900 pounds sterling) for the rights to the Montego name. The Austin Montego (and a sportier MG Montego companion) went on sale in 1984, continuing until its death in 1995 as a Rover. A decade later, the Mercury Montego reemerged as an upmarket twin to the Ford Five Hundred (née Taurus) until the 2008 model year, when then-new Ford CEO Alan Mullaly decreed the return of the Ford Taurus and Mercury Sable badges.
