Finding Your Current Scenario's Average Crop Yield
The best candidates would be 3 to 5 of your most recent crops-as-usual. This simply means to use crops where little or nothing has changed from the way you're now doing things or the resources you're now using. For example, if 3 crops ago you changed something that noticeably affected yield, such as adding light or space, then using your last 3 crops would represent the average of your current scenario much better than the last 5.

Generally speaking, crops-as-usual can have yields that vary +/-15% from the average, so don't expect them to be nearly identical. However, this figure is just a rule-of-thumb. Crops can fluctuate more, especially over the course of a full year when seasons bring unwanted, and sometimes uncontrollable, changes to the indoor environment. Temperature, humidity, and water quality to name a few. For most growers, 3 to 5 crops is sufficient for a workable average.