The turn in the industry during the mid-90s with direct market figures and McFarlane's domination is the end of the vintage era, so TMNT and the end of the GI Joe line should be considered "vintage".
Bronze Age: 1950s-1964, First licensing of characters from media in various forms of dolls and figurines; Marx Toys
Silver Age: 1964-1975, Term action figure coined, GI Joe; Capt. Action; MEGO licensing Marvel, DC, TV figures; James Bond merch; 1st Japanese robots, Shogun Warriors; Oil crisis shrinks figures and...
Golden Age: 1975-1994, In 1975 the Fisher-Price Adv People line is where we first see 3 3/4" with cool vehicles, Star Wars & GI Joe follow suit and become huge. FCC loosens laws of 30 min animated "toy commercials, Masters of the Universe 1st to take advantage and others follow suit, Super Powers/Secret Wars; Japanese import domination with Transformers, Robotech, Voltron, etc. Licenses that will remain in the toy aisles for the rest of our days. License-based Cons begin to pop-up
Industry Age: 1994-2001, Direct market figures to comic shops; Internet & Ebay shopping; figures become "collectable"; McFarlane; Sideshow; Toy Biz; figures carried by video game and entertainment stores; short-packing; multiple versions and repaints (see: your local flea market)
Modern Age: 2001-Now, Small brick/mortars close, Internet marketplace explodes; Marvel Legends; DC Direct; Hot Toys; Medicom; 1/6 figures become new pinnacle of quality and detail; High-quality Anniversary throwbacks (TF, GI Joe, He-Man), re-productions of 12 inch GI Joes, Mego-style figures, Captain Action; 80s licenses dominate still (SW, GI Joe, TF)
Artist Age: Now-?, Customizing from 3 3/4" Joes to Justice League to Marvel Legends to 1/6 scale