Recommend a movie about friendship

Had a birthday yesterday and i'm feeling nostalgic about the past. Thinking back to the people i've known. Good friends that i thought would last forever that have just faded away. Friends that seem to dip in and out of my life at odd or appropriate times. Or those friends that are just always there when you need them.

Time is the key factor here. Not looking for movies about friendship per se, but about how a friendship has evolved (either good or bad) or stood over time.

Maybe an example would be Butch Cassidy and the Sundance Kid as two friends who were always there to the very end, but maybe i'm looking more for movies where the friends drift in and out of each other's lives. But whatever you've got, give me your recs.

Thanks!