Most will start seeing dental issues with untreated tooth decay in the beginning or during their 30's, which equates roughly 2 decades of mistreatment. If accelerated, in your 20's after 1 decade.

Assuming you're not predisposed to other issues and that you still brush your teeth at least once a day most of the time, that's the speed of decay you should expect and the timelines you're working with. The daily, monthly or even yearly progression is miniscule, making it difficult to observe if it has been slowed or halted, especially in messy anecdotal tests.

The exception being tooth grinding, which can go faster and is easy to measure.