The term "vinyls", at least as applied to analog records containing music, is a non-sequitur and a non-word. It has arisen in the last 5-8 years with increased hipster-youth interest in the LP format. It was never, ever used by any coherent native English speaker before this time, particularly when records were the dominant format. Using "vinyls" now isn't a great idea for your credibility either.
Whether you buy one record, or five, or fifty, or five hundred, you have just purchased vinyl. Regardless of whether you have purchased one record or multiple records, you have not purchased "vinyls." Going around telling people about all your new "vinyls" just makes you look dumb to anyone who has the slightest clue about the physical distribution of recorded music... or English grammar.
FAQ:
Q: "Why is the use of 'vinyls' grammatically unsound?"
A: Vinyl, formally known as polyvinyl chloride, is a singular substance with a universally accepted chemical definition. Records are pressed onto vinyl. Whether you walk out of the record store with a single 180-gram pressing or 180 kilograms' worth of records, you are still holding a volume of vinyl (in cardboard sleeves) in your hands.
You most likely would not refer to a singular album split across two or more vinyl discs as being available "on vinyls" (nor should you). You would not refer to a single session of filling up your car as buying "gasolines" (or, for Brits and Aussies, "petrols"). You would not talk about using "soaps" to wash your hands using the homogenous supply of liquid soap in the gas-station bathroom, even if you had to hit the gas-station soap-dispense button more than once to get the job done. Nor would you publicly refer to drinking multiple milliliters' worth of soda in a single can as "drinking some Cokes"... at least, not if you wanted to present an image of having an IQ over 75.
And-- praise Jesus, praise Him-- while the term "on wax" has been a long-accepted (if admittedly chemically misleading) colloquialism for a recording available in the analog-disc format, you sure don't hear anyone going around talking about a trip to the record store to "buy a stack of waxes."
...At least, not f'ng yet.
Q: "What term should I use instead? I really want people to know that I bought (or own) more than one record!"
A: Suggested alternatives for those who just have to get the notion of quantity-purchase or -ownership across: "records", "LPs" (at least if you purchased records in that particular format), or "a great heaping helping / metric s***-ton / etc. of vinyl". If you want to impress others with your super-old-school skills, at the risk of sounding completely pretentious, you could also try something like "phonodiscs".
Q: "Is it still OK to say that, when I purchase a single record, I have just purchased 'a vinyl'?"
A: No. This usage, while perhaps not quite as grammatically questionable, is also a tragic invention of the latest young crop of music buyers, who grew up hearing things like "I just bought a CD." That quoted sentence is correct, since it uses the trade name of the actual format-- the CD, aka the Compact Disc-- rather than referencing the raw materials used to make the CD medium itself. The CD equivalent to "I just bought a vinyl" would be: "I just bought a polycarbonate-and-aluminum." Sounds totally f'n stupid, doesn't it? Exactly my point. So: you just bought a record or an album or an EP or a single, which you just happened to purchase on vinyl.
Q: "Is it true that no one ever used the term 'vinyls' (or the aforementioned phrase 'a vinyl') before records became fashionable again in the mid-2000s?"
A: Yes. Accordingly, using either of these terms around anyone over the age of 30 and/or your friendly local record store clerk pretty much guarantees they will want to stab you in the face.
Q: "But I have heard other people call them 'vinyls'."
A: Those people are also wrong, and their abuse of accepted English should not serve as a justification nor an inspiration to anyone. Note that while the RIAA is decently ecstatic about the newfound popularity of the now-very-expensive and highly profitable vinyl format, no one in credible positions associated with the record industry on one level or another has ever made a statement about the "comeback of vinyls." The term "vinyls" is only used by people who just bought their first analog phonograph record a month ago and have no idea what they are talking about.
Q: "Wait, are you arguing that language should never evolve?"
A: No, I am not arguing against the evolution of language. I am, however, arguing against the needless, thoughtless and syntactically broken evolution of language brought about by sheer ignorance. Fact: No one who knows / cares a whit about records and/or the storied history of the format should ever use the word "vinyls".
Any further objections? Please immediately contact Steve Albini, who will probably do a better job than I ever could at ripping you a new asshole.
A public service announcement from the Loss Foundation
Now that you have been sufficiently educated, come join the parade of "vinyls"-user shame.