Agreed with this.
I've pretty much abandoned my first character aside form maxxing out their main crew skill. I just felt bored every time I played them (Sentinel). Many different reasons why. I will go back eventually though and gear them up, respec to something more interesting and play again. Maybe try doing something different for xp. I've also got a high 40s I'm not playing with, but not abandoned. I enjoy playing them a lot (Commando/healing/4X) but once I hit 50 I know I will lose interest. I also enjoy the planet they're on and don't want to leave it lol.
Agreed with the others as well, change their gear, respec, try different companions. Or just reroll and come back to them later.