Boogie Nights is a portrait of the porn industry in the late 1970-beginning of 1980s. Using John Holmes as the main 'character' the movie attempts to realistically display the up and down of a porn career, from the 'discovery' to the 'self-destruction' and perhap the 'recovery' at least morally. But if you take apart Holmes character, the movie had a more general feeling of what a 'career' in porn may look like. In my view this is the real beauty of Boogie Nights, and in this sense the movie is way superior to the self-portraits attempted by the porn industry in hundreds of flick (there is long list of movies that attempt to describe the 'behind the scenes - e.g the manipulation of the stars, the drug-infested atmosphere, the hype of the big (tits, penis, butts, etc.), the exchange of favoritism, the corruption of casting agencies, of the directors, and of the entire film productiion chains, etc. etc.
In this sense the movie is a portrait of the dark side of the Golden Age of Porn, but its validity as all good movies is behind its specific temporality. Holmes was the man who became a sensation not because of his big and long shaft, but because that it symbolically captured and incorporate what porn industry live on: namely, the craving for HYPE.
In regard to the Golden Age of Porn: Temporally it started with Deep Throat (1972) and in my view it ended in 1985 when New Waves Hookers was released: The Dark masterpiece initiated the 'Wall-to-Wall' style of porn-making, completely destroying the 'plot-style' that was the high mark of the Golden Age.
New Wave Hookeers totally demolished the 'aura' of intellectualism, sophistication and social meaning that decorated so many Golden Age flicks and it opened up the gates of 'hard/fast and furious' sex, where the 'bodily action' it became the beginning and the end of any porn flick.