system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars: TFA] Why doesn't Anakin/Vader just go force ghost and tell Kylo to chill the fuck out?
gpt
In Legends, at least, the ghosts of Jedi couldn't stick around forever. Obi-Wan's ghost told Luke he had to move on after only about a decade and a half.

In canon, we haven't seen how long they can last - we have the disembodied voice/spirit of Qui-Gon lasting to the end of the Clone Wars, thirteen years after his death, but that's the longest-lasting spirit we have as of now.

But - there is one thing we do know. Anakin redeemed himself on the second Death Star. He wasn't a Sith anymore. And Sith can't become Force ghosts anyway.