One of the most asked questions regarding Frequent Flier Programs is, “How do I avoid losing my miles?
It’s important to know that all Frequent Flier Programs have rules and regulations on using the miles you’ve accumulated and the life of your miles. While they differ by airline, there are some similarities. And one is “your miles will expire if there is no account activity within a certain period”. The key point here is account activity!
Account activity means more than flying on the airline or its partners; although that is one of the surer ways. Account activity means ANY account activity during a period.
This activity could come from shopping for groceries, using your credit card, buying flowers or buying gas, just to name a few. So, check with companies you currently do business with to see if you can link your Frequent Flier Program if you haven’t already done so.
Get an airline credit card so that every purchase you make with it earns miles.
You can purchase additional miles to keep your account and miles active.
Some airlines allow you to donate some of your miles just to keep them active. And, if you lose miles, you just might be able to reinstate them, at a cost of course.
You can also link your airline program with your hotel program.
Since the rules and conditions of your frequent flyer program vary by airline, it would behoove you to know the rules and conditions of the programs you have. Some expire in as little as 3 months like Spirit 
and some never expire like Delta. 
To keep tabs on your account, signup for email and text alerts and put those expiration dates on your personal calendar. They will usually alert you when and if your miles are about to expire.
Ja’Vonne