Yup they re-released them several times. Original Star Wars was May 1977 and I know I saw it then, but it was also definitely showing in theaters at Christmastime in 1977 because I have pictures of my 6th birthday at the Fox Triplex Theater in Austin, when we went to see Star Wars. My birthday is Dec 7.
Searching the internet, there's no record of a Christmas re-release, so it either wasn't widespread, or it had just stayed in theaters for all that time. Which is a possibility, movies used to have a much longer theater run than they do now, for various reasons.