If you have detectors that only have options Manual soil balancer, then you'd better do the soil balance if you see that the soil or the conditions where you detect change. or you can do the soil balance if you feel that the detectors are less clear and unstable.

If you have detectors with Automatic soil balance, you don't have to do soil balance too often, basically just before you start detecting.

However, my personal recommendation was to do land balance when soil conditions change significantly, better to do it than not to do it.