How long did Luke know Ben, in the context of the OT?

To me, it always felt like they knew each other for awhile, but couldn’t see each other often because of Owen. They seem familiar with one another in their scenes together.

“Ben! Boy am I glad to see you.”

“Tell me young Luke, what brings you out this far?”

Whether or not they knew each other for awhile, I’ve never agreed with the criticism of Luke for being too sad when he dies. Luke is a person who grows to care for people fast. Likely because he doesn’t seem to have many friends on Tatooine left.

Luke about R2 near the end of the movie, after a couple days with him:
“Not on your life! That little droid and I have been through a lot together.”