It's very interesting to look back on the earlier designs of your characters you actively develop to this day.
getting reminded how far you've come as an artist, and as a designer, motivates me greatly :).
below, you can see some examples of the evolution my characters have gone through.

pictured: manifesto, Smeshnoy, Vincent, Ambriel, Marlowe.

Here's another picture containing my oldest proper OC Galaxia. happy 7th birthday girl!!!
Some characters went through such drastic changes, some way less, still i'm proud where i am right now ^.^!! hard to believe it's been 5 years!!!
I recommend doing a timeline like this, It's a fun time capsule.