Every ceramic coated header I've installed on customers cars did exactly what yours is only sooner. The only exception being jet hot or VHT. Myself I prefer the VHT. have a set on my 38 that were done ~ 30 years ago and no issues. The car does not see daily use but has racked up 10k or so miles. the other 2 items i like are
1. the cost, 2. easily touched up if needed. I use the SP117 flat aluminum.