The answer depends on the type of application. See some examples.
1. Simple installations
Simple installations with one battery (12V) or with just a few cells do not need any special inspections. If you have an SMB to handle the protection of the pack, you can just monitor the voltage level. This kind of pack should be inspected once or two times a year. Or perhaps each time after a long pause in usage. Note: do not forget to disconnect all electronics if not using the pack. The pack should have dual protection, as explained here.
2. Advanced installations
More advanced installations (typically with 8 cells and more) should be monitored regularly. It is recommended that the inspection of the pack is performed in these intervals (ie, after a number of discharge/charge cycles):
For example: for the battery storage applications (typically with 1 cycle/day), it is recommended that the inspection is done every 100 cycles, which means about every 3 months.
The advanced installations need to have multiple protection to avoid accidental discharge or overcharge of the battery pack.
3. High voltage installation, high power installations
The most advanced industrial applications, including energy storage systems, traction systems, etc. should have a continuous monitoring of the battery pack and the status of the cells. This is typically done by means of an advanced BMS together with some secondary or tertiary monitoring and inspection. In such applications, the cells and monitored continually and the inspection is organized according to the operational design plan.
More info
See also the overview of the initial-charging FAQ