We all struggle with that as our volume grows, but here’s the approach I take:
I don’t respond as quickly if someone is simply chatting after a few messages, and it’s more apparent they just want to talk and there isn’t a personal connection. Half the time the slower responses cut the message flow.
After things stretch out a little, and it took me hours to respond, I say something like this:
I don’t mean to be rude, but when I’m recording/working, I don’t respond very quickly unless someone has a question directly related to an existing order. I have a rule that existing clients, and order(s) in process take priority over potential clients. At first that may appear rude and less responsive.
My focus is existing customers first. When you have an active order you will appreciate that because the focus will be on your gig. IF it takes me a while to respond, you’ll know I’m working on an order for someone else. Occasionally I lose a potential client, but the ones I have appreciate my focus on their work, and they keep returning because they get great service.
I love my existing clients, and someday soon I hope you’re in that group and my focus is on your project.
If they keep sending while I’m working on their project, I just say “Sorry, while I’m working on gigs I have to stay focused, so my response time isn’t as quick. If you have something time sensitive, please be sure you state that in your message.”
As it stretches out, few keep sending me additional messages.
I don’t say that word for word, but that’s my policy, so it works for me. YMMV.