I find it extremely helpful to revisit old drawings and revamp them. Call it OCD or just plain old perfectionism, I am subjected to this annoying thing of trying to outdo myself day in and day out.
Here's a little example of what I mean. When I first created the Funnicks, these two characters interacted on a skit with boxes. Well, after a year, here they are together again in an episode similar to their first debut.
Characters evolve and it is fun to see this evolution in progress. Sometimes the changes are so subtle that you can barely tell unless you compare a recent with an old version such as the evolution of Mario and Mickey Mouse shown below.