Live Long and Prosper
When someone greets you with “live long and prosper,” they are telling you to have a good one, and they'll catch you later.
It's a “Vulcan” saying out of the Star Trek franchise, popularized by “Dr. Spock.” Today, many “Trekkies” use the saying when they say goodbye to each other.
'Live long and prosper is an abbreviated version of a traditional Jewish religious blessing.