look at the history of technology, and before that to the biological history - how long it took from single cells to multi-cells vs. for example how long it took from lizard brain to human brain - the things are naturally going exponential (my thinking why - https://news.ycombinator.com/item?id=9418811) at least until they hit some wall, yet so far hitting walls mostly only stimulated even more advanced development.

There is an issue of the "non-uniformity of the spread of the future" though with fast development, and the faster the development the stronger the non-uniformity and the tensions it creates. Strong non-uniformity and resulting tensions have tendency to resolve catastrophically on their own at some point if not solved/smoothed by the other ways before.