In this context, maturation doesn't refer to the age of the person, but the of wear.

Usually involves wearing the same pair of panties for 12 to 48 hours.

Texture and volume change based on the menstrual cycle, hydration, and arousal levels. 🎒 The Panty-Selling Industry

Cotton is often preferred by wearers for health, though synthetic fabrics (like nylon) are sometimes preferred by collectors for how they display the "creamy" texture.

The "cream" is simply natural , which is a healthy sign of a functioning reproductive system.

Buyers often look for "matured" items because the stains and scents serve as proof of wear.

Body heat and natural moisture cause secretions to thicken and oxidize.

This topic is a major cornerstone of the "used panty" marketplace.