The Repeat Secondary Characters In A Mystery Series

I've been working my way the through the final edits on my new P.I. Frank Johnson title (#7 in the series), and I've noticed several of the secondary characters have appeared in all or most of the previous titles. That got me to thinking about the repeat secondary characters. They are as important as the protagonist is to make the series a successful continuation. I like seeing the familiar face(s) come up in a series novel because I feel like I already know them. I may or may not particularly like them, but I am reassured to know they are still around. They are like the guideposts to look for. I like to have Frank interact with his friends and loved ones. My favorite of the secondary characters is his sidekick, Gerald Peyton, who is a bounty hunter with a reckless, fearless streak a mile wide. They play off each other well. One thing I have resisted doing is having Gerald do the dirty work that Frank won't do. After all, partners share everything, even the bad stuff. I hope Frank and Gerald will be around for a few more adventures. They have been fun company for me.