Coconutzz

Hi everyone first time posting here, I just finished reading WOK and WOR (my first Sanderson books) both of which I absolutely loved. When I found out that book 3 was still months away I went on a Coppermind spree and was just amazed by the scope of the Cosmere. I really need to start reading the rest of Sanderson's novels. Anyways, I stumbled upon the Shattering's page where it read "Brandon has stated that he currently imagines it[the shattering] to be about 6,000 years before the Stormlight Archive Prelude, or 11,000 years before The Way of Kings" To my understanding Odium went about killing other shards after the shattering. I assume this took some time so it is unlikely that he started the Desolations immediately after the shattering. However, let's say that Odium did in fact begin desolating Roshar right after the shattering. 6000 (years before the prelude) divided by 99 (desolations) gives us = Roughly 60 years between desolations. This brings me to my 2 questions. 1) Why is it that the most recent period between desolations has lasted 4500 years? Previous periods were definitely shorter and there were 10 heralds as compared to only 1 now. 2) Many times in the books it is referenced that much knowledge is lost between desolations. How is that possible? A teen aged 20 during a desolation would be 80 by the time his/her second desolation came. He/she would pass along firsthand knowledge of the desolation to his children and grandchildren. Assuming his descendants survived their first desolation they would realise "rust, gramps wasn't lying, we should probably prepare for another desolation" In this way surely knowledge like being able to cast bronze would be retained through communities, let alone kingdoms. Apologies if this topic has been done before or if I am using outdated info. Thanks!