6 months maybe.
A lot of bands took off in '68 -69 doing their own versions of psychedelic mood rock. King Crimson, Hawkwind, The Nice were very quick to develop their own progressive rock sound. Hawkwind took the psychedelic rock road way further than Pink Floyd did. And as far as I know they are still going. Interestingly enough it's only in hindsight that we see Pink Floyd as a great progressive rock band. During the late 60's and prior to '73 (Dark side of the moon) very few people knew who they were. I remember loving Obsured By Clouds when it came out, and no one I knew had even heard of them before. Dark side of the moon changed that. But even then, I don't remember it launching them into mega, instant stardom. By the Wall. They were bib, big, big. Up until that time they were considered underground.
Anyway, that's how I remember it.