PreCheck frequency based on flight frequency?
 

For the first 7 months of the year, I flew 88 segments and got pre-check literally every time it was offered. I hadn't flew since July and today I didn't get pre-check. Is pre-check linked to the frequency of flights?

No...

TSA made it very clear in the beginning that this is a random process. Some flyers qualify nearly every time, some only rarely. Not enough data points to understand why it works sometimes but not all times, but this is exactly what TSA intended. Some go for long periods without PreCheck qualifying.