How often do you or your clients manually read their meters? What problems do you face when doing this?

Generally, a meter with loads of 20 kVA up to 100 kVA invites annual testing while those above 100 kVA every three, six or twelve months based on load category and domestic meters every five years.  In order to ensure that the bills are accurate, it is advisable to check the meters every month.  However, since there is no interference of any kind and that it is as per consumption, a check once in a way should be fine.  This is because evaluation of normal monthly consumption patterns and payment are ideal indicators as it is a routine exercise.  However, one would surely understand the deviations from this routine billing and can lodge a complaint.

A simple test on turning one facility and checking the meter speed to compare with multiple facilities would indicate meter performance.

Smart meters could be designed for half an hour, once a day or even once a month depending upon the utility and requirement.  Meter calibration is also important and as a rule, it is 10 years for newly approved induction meters and up to 20 years for static meters.

Here’s a 2019 link for good metering resources.   https://www.eei.org/about/meetings/Meeting_Documents/2019-Fall-TDMMA-Metering%20FINAL%20Agenda-Minneapolis.pdf

I quote a section on meter reading from a Minnesota distribution utility's Integrated Distribution Plan (IDP):

"Otter Tail’s business case for deployment of AMI is expected to be favorable. One factor
supporting AMI deployment is that Otter Tail is not moving from an Automated Meter Reading
(AMR) system to an AMI system. The Company’s service representatives will be more efficient
and more capable of providing real time information to customers if a customer does call with
an electric use question."

Another MN distribution utility says this in their IDP:

"Minnesota Power uses four different methods to monitor and control its distribution system:
Supervisory Control and Data Acquisition, smart sensors, automated/advanced meter collection,
and manual meter reading"

The extent of manual meter reading is often discussed in public filings related to AMI investments rate cases.  For example, on Monday, March 15, 2021, The Michigan Public Service Commission said the agree with DTE's recommendation to charge a fee to OPT OUT of the AMI program.