Like most of you, if I message them it's almost always about booking or something related. I rarely start a convo unless it's something that'll likely be short. I don't want to intrude on their personal time, and I don't know if they're around other people or someone else has access to their phone.
I have a few that message me from time to time, and then I'll get into longer convos with them since they started it. I've actually had a couple of SPs ask why I don't text them more often. I told them the reasons above, and they said not to worry about that and they want to hear from me.