A Repeat Customer Insights customer was asking about comparing two different years. The problem was that one year wasn't completed yet.
Comparing years is usually a great idea but you have make sure they are the same length. If the year's not over yet, then the absolute metrics will be off (e.g. less orders) and some of the time-based ones will be weaker due to the shorter timespan (e.g. 365 days vs 185 days).
You can adjust the absolutes with a bit of forecasting and projecting, e.g. nine months of data so guess what the remaining three will be like. Just know that any forecast is going to be off and most ecommerce businesses show seasonal patterns that throw off forecasts even more.
A quick and automatic way to measure your customer behavior is with Repeat Customer Insights. It'll automatically import your Shopify data and run a number of analyses to highlight different customer behavior.
Learn which products lead to the customers who spend the most
You can use the First Product Analysis in Repeat Customer Insights to see which products lead to the customers who spend the most. Going beyond best sellers, it looks at the long-term purchasing behavior of your customers.