Using character names for books?

So, I write stuff like short stories, novels, etc. I've used the two names Seth and Kayla for main characters in, I think, 4 of my stories. None of the stories are related to each other, and the characters always have a different background, look, personality, relationship, etc. Is this an "okay" thing to do? I'm not going to use them all the time, but I have used them a lot.