Plato said the prime of life doesn't even start until you're 25 and Schopenhauer said something similar (can't recall his exact number). You can still learn and grow a lot way later into life than most people think. If you really care, just try different techniques, measure/test yourself, and continue the cycle. If you can't find the motivation, maybe it's just actually not that important to you, and deep down you have greater interest in other things than learning how to type fast.