I was asked recently:
How often does customer behavior change?
Every day new people can decide to become your customers.
Every day current customers can decide they are happy with your products and check back to see what you're selling.
Every day past customers can decide to try out a competitor.
Not every customer changes every day, even in the fastest moving industries. But every day your customer base changes. Some tiny changes that you can't detect. Some big changes that you can if you're looking for them.
That's why it's important to be continually analyzing your data with Repeat Customer Insights or your own system. There's a lot of changes you miss if you only look every few months.
This is also why I recommend setting aside a dedicated time each week to review. I recommend Mondays because that's when the Monday Morning Metrics are emailed out. That's a good summary of the week and a way to start your analysis conversations.