Measure Customer Loyalty
Measuring customer "satisfaction" isn't a very effective method for knowing what percentage of customers will continue buying from you. A customer who is only "satisfied" rather than "highly loyal" or "thrilled" could easily defect.
It's better to think in terms of loyalty and future intent: Do they intend to continue buying from you? Will they recommend you to others? One of the best ways to ascertain this is by asking your customers to complete a survey.
To quantify your loyalty by your customer segments, you can rate them on the recency of purchases, frequency of purchases, and the total money spent. Once you have a numerical value, you can tell which segments are most loyal, and which need attention.