If the paint is in great shape and you like the color, then don't bother painting.
If the paint is in great shape and you don't like the color, then paint the bike.
If the paint is beat up but not too bad and you like the color, then don't paint the bike.
If the paint is beat and you think the color and finish looks terrible, then paint the bike.
If the paint is in great shape and you like the color, but want a more durable finish, have the bike powdercoated.
If the paint is in great shape and you don't like the color and want a more durable finish anyway, have the bike powdercoated.