Points expire automatically. If you renew early for the next period, the unused days of your current month's usage can be carried over to the next month. For example, if you recharged 1.2 million points in January, used 200,000 points on January 10th, leaving 1 million points, according to the formula: 1,200,000 / 30 days = 40,000 points of usage per day, then the maximum amount that can be replenished is: Remaining days 20 days 40,000 = 800,000 points. If 800,000 points have already been used by the 10th, then the maximum amount that can be replenished is 400,000 points.
PS: If you switch to another plan, such as from 99U to 49.9U, you cannot transfer the remaining credits.