Going into the end of the year you'll want to compare a few metrics to last year and the year before to see how things have changed.
- Total sales
- Average Over Value - good if it stays consistent or has gone up. Great if that happens while total sales have gone up.
- Repeat Purchase Rate - should be trending up when looking at the full history (the "All-time" in Repeat Customer Insights). Okay if it's consistent on a year-over-year basis.
- Average number of orders per month - should trend upwards.
- Average Latency - good if it's getting lower.
These metrics will interfere with each other too so you'll have to done some reasoning about them.
For example, if the Average Latency went down (good) but Average Order Value also went down (bad), that sounds like customers are placing smaller, more frequent orders. In most cases that would be great but it could be a problem if you have a high per-transaction cost (e.g. credit card fees, high pick and pack costs)
The COVID pandemic will also have bumped 2020's ecommerce orders up so you'll want to analyze the trends from 2019 and 2021 directly, ignoring 2020 as an outlier. A drop from 2020 to 2021 could just be from ecommerce getting back to a more normal level.
Many of these metrics are available in Repeat Customer Insights along with automatically filtered years, depending on your account level.