Once you've built up trust with customers, they are more likely to buy faster and more frequently.
Normally repeat purchases should occur sooner and faster as a customer is more familiar with your brand. e.g. the third purchase will happen sooner than the second.
It's recommended to compare how the first six purchases vary in the order timing.
Are the delays decreasing (good)? Are they increasing (bad)? Or are they varying wildly (bad)?
If they are increasing or vary from order to order, this is a symptom that could point to a weak new customer process.
There are a lot of things you can do to fix this and shore up this part of your repeat customer funnel.
One I recommend is creating a loyalty program where a customer is rewarded for each of the first six purchases with an incentive to order again, maybe even withing a set time period (e.g. 30 days). This gives them an incentive to make all six purchases and to make them sooner than their default behavior would be.
This sort of analysis is one that the Customer Purchase Latency from Repeat Customer Insights is designed to help you with.
Customer behavior analysis for better Shopify store performance
The Shopify App that increases repeat customer purchases through customer behavior analysis.