I usually refer to each film by its Episode, or one word of the title, ie; “Menace, Clones, Sith, Hope, Empire, Jedi, Awakens.” But if I’m online I’ll usually abbreviate the subtitles (TPM, ANH, TFA).
I tend to use the Episode number more though.
It’s probably because I’m in my 20s, I grew up with the '97 SE and the Prequels so I guess I’m more used to it.

I was quite disappointed TFA dropped the Episode subtitle from everything except the crawl though. I’m a massive Star Wars home video collector first and foremost so having almost every single DVD have the numbers on the spine and match up nicely, it makes TFA look even more out of place.
Not a fan of the cover art of TFA for the DVD/BD in general actually. But alas, I’m getting off track now.