Mine used to be very random in their phone calls. Sometimes I heard from all three of them on the same day, sometimes no-one for a fortnight. I decided to rationalise this, and asked them if they could try to each phone me once a week, each on a different day. This worked very well with two of them, not so well for the third, who isn't so good at remembering, so I started ringing her one a week instead. By the time Covid struck the world and we were into lockdown, we had a good system in place - contact at least three times a week, nicely spaced, and info about each of them passed on to the others via Mum's news agency.