And keep in mind, you're in FM. I believe the poster you're speaking to is in psych. As an attending psychiatrist, I would never tell patients they can reach me day, night, holidays or weekends (unless I had a concierge practice). Many, if not most, psych patients don't consider "medical" urgency when making calls, especially the personality disordered ones. They sometimes call because of a breakup or because someone was rude to them. I tell my patients to call me if they need me and I generally return phone calls the same business day. If they need something outside of business hours, there is an on-call psychiatrist only for emergencies (and that person knows how to get a hold of me if needed, but I don't tell patients this part). If they're in crisis or unsafe, they need to go to the ER, not wait for me to call them back. The ER will notify me if necessary.
But psych is generally different in that depending on patient population, it can actually be harmful to the patient's treatment plan for me to be at the patient's beck and call. I see a lot of personality disordered patient. No easier way for a borderline or dependent personality to decompensate when I am out of town or legitimately unreachable than if I set the precedent that I will always be there for them.