Post-Braces: Should I Replace a Long-Missing Premolar or Just Leave It?

Hi r/askdentist,
I'm a 39-year-old male, non-smoker, and I just finished orthodontic treatment with braces. I have a missing lower left premolar (next to the canine) that’s been gone for over 20 years. It's barely visible when I smile.

Now that my braces are off, I'm debating whether to get a Maryland bridge (resin-bonded bridge) or leave the gap as-is. I’m not interested in an implant — it feels too invasive, and the space is smaller than a normal premolar gap.

If I choose not to replace the tooth and just wear my retainer at night, is there a good chance my lower teeth will stay aligned long-term? Or is there a risk they'll shift back over time?

Any insight or suggestions would be really appreciated. Thanks!