Insulation does not have a "check engine" light. Homeowners often assume the white fluff in their attic lasts forever. Reality is much harsher: gravity, high humidity, and rodents actively degrade your thermal envelope year over year, secretly bleeding hundreds of dollars off your HVAC efficiency.
Fiberglass Settling
By year 15, blown-in fiberglass will have usually settled by 10-15%. What was once an R-38 depth has likely compressed down to an R-30.
Code Obsolescence
Texas building codes adapt. Homes built in the early 2000s were only mandated to hit R-30. Today's code is R-38 or R-49. At 20 years, your house is technically outdated and bleeding efficiency vs modern standards.
Contamination Events
If you have had a severe roof leak, or a confirmed rodent/raccoon infestation, the lifespan drops to zero immediately. Urine-soaked insulation cannot be saved; it must be extracted for indoor air quality.
Grab a tape measure and stick it straight down into your attic fluff until it hits the drywall ceiling. If the depth is less than 10 to 12 inches, your lifespan is over. You are actively losing money to Oncor every month.