Aside for cosmetic reasons, is it a good idea to replace a 12 year fork? The fork in question is a Columbus Tusk. Safety at this point is the primary concern since there is no way to easily inspect the carbon steering tube. Might as well just replace rather than doing all that work to reinstall an old fork.

if you know the fork hasn’t suffered any trauma, there’s really no need to replace it just because. However, if you’re concerned about it, for whatever reason, then the cost of a new fork is worth it. I replaced mine after 13 years - the bike had suffered a “garage dooring” incident, and while the fork looked OK, I didn’t feel that I could trust it, so I replaced it. I may have junked a perfectly good fork, but I wasn’t comfortable with it, so it had to go.

If its possibly damaged, then replace it. If there is no concern, then don't replace it. Pretty simple.

My 9yo was out riding with me today and her road bike has a full carbon fork thats 12 years old. I dont think teice about her using it as it was in good condition when we got the bike a handful of years ago and has been handled well ever since.
0 desire to change a fork that is giving me no reason to want to change it.

I justify replacing one if I am converting something over that necessitates the change, flaw that I perceive no longer reliable for my use, or feel like a change is needed. Been looking at converting my suspension fork to a fixed fork, but with the current price gouging & parts production delays, I'll probably not get around to it any time soon unless I find a used one that I like.