Are you in need of cash? Sell it.
Are you financially comfortable, and enjoy collecting basses? Keep it.
Could you find another piece of gear you would enjoy more with funds from the sale? Maybe sell it.
I had a bespoke/custom bass that I dumped a LOT of money into. I finally admitted I just never jived with it. I got out of it what I put into it and bought 3 other basses that I REALLY enjoy playing so much more.
The value of the bass I sold keeps going up, and I have watched it trade hands 3x since selling it, each time for more $ than the last. I'm not mad about it, and I wish each owner of it well! I'm just down here having a blast with a bunch of new Japanese Fenders, lol!
I am 41, and dealing with the decline of my parents. My Dad is now in memory care down the street, and I am trying to help my Mom deal with life essentially on her own now, after 53 years of them being together. My Mom is a pack rat, and I am seeing now how holding on to so much crap because "It might be worth something one day!" has really sucked so much joy out of her life... not just in the past, but the present and whatever time she has left, too.
I have the same hoarding tendencies she has, and am really trying to come to terms with all of it. I want to maximize my positive impact on those around me, grow my relationships with family and friends, and get the most enjoyment out of my hobby stuffs. I am working to save enough that hopefully I won't need my bass values for retirement. I'm seeing that I already have some unnecessary stuff that weighs me down, and I have made my wife so proud with how much stuff I have gotten rid of, haha! It is freeing and a breath of fresh air every time another pile of stuff disappears! A couple weeks ago I gave a box full of about a dozen lower-priced (like $40-100ea new) guitar pedals to a budding guitar player I know. I hadn't used them in years as I've moved on to better/different stuff. Sure, I could trade them in at GC for a pack of strings, or deal with the nightmare that is FB marketplace... but the joy of helping him get to learn and play with new gear was so much more rewarding to me.
Phew... detour, sorry. Back to the equestrian at hand: if you enjoy owning it, keep it. If it's just sitting there and you could get better/more life fulfillment if it were turned into another form of value (another bass, a vacation, new/classic car, or doing something great and meaningful for a friend or loved one) then do that! Let the retirement account handle that side of things, and let your hobbies improve your life.