In TLJ, the remnants of the Resistance fleet head for what Leia says is an abandoned Rebel base on Crait.
Why was the rebel base on Crait abandoned?
- Had it been discovered by the Empire?
- Was it too small, too remote, or too inhospitable to be worth keeping?
- Did the Rebels regularly abandon bases as a security measure, sort of like changing your password every six months? Considering that the Rebel base on Dantooine had apparently been abandoned for some time before its discovery by the Empire (in ANH), it seems plausible that regular base rotation is a standard Rebel practice, but it seems awfully expensive.