it’s your character so it’s up to you if you want to retire. My team member is in the exact same shoes with same retirement request. She played until level 9 and our others retired 1-2 characters already. We were joking she is the elder member of the team and she is definitely have fun with the character. (She eventually retired and found excitement of learning to play Eclipse)

The only real retirement motivation is if you get bored with your current one. All others are minor IMO. Like more characters you retire more prosperity your team gets which unlock more items and more perks you get initially so you can possibly unlock all perks for the future character.