Cultivated diamonds are exactly the same as mined diamonds and do not fade over time.
Cultivated diamonds are real diamonds with the same atomic structure as mined diamonds and are the same - physically, chemically & optically as mined diamonds.
So if mined diamonds or naturally sourced diamonds do not become dull overtime, neither do created diamonds. In fact, lab-grown diamonds have the same shine, sparkle, brilliance and dazzle of a mined diamond.
We all know that the brilliance of a diamond lies in its cut. And apart from the growth process (in the earth’s belly vs. in a laboratory), every other process followed is the same whether in mined or lab grown diamonds. Which means, the rough diamonds have to go through an evaluation process to figure what kind of diamonds can it yield, cutting and polishing to create dazzling beauties. This is the part of the process that ensures the dazzle and fire of a diamond which is true for both the diamonds- mined and created.
The only circumstance under which any diamond becomes dull is due to improper care which causes scratches and blemishes on the diamond. Rough use like using chemicals like perfumes, detergents, lotions etc. on diamond jewellery, wearing diamond jewellery during heavy lifting, exercising, swimming etc. can cause damage even to the hardest substance on earth. When a diamond is bruised, it affects its light performance which makes it seem like it has become dull. Diamond jewellery is not stored properly and cleaned gently regularly, gathers grime and dust and starts to look dull. Again, this is because the light performance of the diamonds are affected due to accumulation of dirt. This is true for any kind of real diamond, whether mined or man-made.
Taking good care of your diamonds will ensure that it never gets dull overtime, whether a nature created or lab created diamond.