The first time I heard the phrase "by and by" was in the song Broken Halos, by Chris Stapleton. I could tell by how it was used; he was talking about another world, dimension, or time. It was a different place he was referring to, like heaven.
I had to look it up because what a fantastic set of words to describe an unknown space, time, or place for a character in one of my stories. Here's what I found out.
• Dictionary says is means before long; eventually
• Websters Dictionary adds to that with a future time or occasion.
• The Free Dictionary adds even more with the unknown future, especially heaven or the afterlife.
It seems that this phrase can be used relatively loosely since it's sometime in the future, some other place, or the unknown. Sounds like a great place for one of my characters to disappear to for some alone time.