I'm 29, and I have already started feeling this. Just a few years ago, I could do 12-14h coding days sustainably, but now, anything above 11h sustained for weeks really shows in my output quality. Luckily, my overall productivity is still rising due to learning and experience, despite the degrading mental capabilities. I don't know what me at 35 will look like. I now see where the ageism comes from.
I find it incredibly sad that I even need to think about this. I regret that I even participated in this circus in the first place. I now only work for companies with don't have the ass-in-seats-for-80h policy. It's actually interesting that in startups where this works, people self-select and end up there. It's amazing how much more you can achieve if you can afford to take a step back, and not worry how you can run in circles even farther and faster.
Also, if you transform bag-of-words vectors into a dense form, you're gonna have a bad time (insert appropriate meme picture here). In large corpora, dimensionality grows quite substantially - if you work with news corpora or Wikipedia, you're in the 100k-1M dimensional space pretty quickly.
Great to see an approachable explanation for NLP. As they say sometimes, when you know how it's done, it stops being "Artificial Intelligence".
I solved this by using the "Insomniac" approach - if you play a silent sound every 30 seconds or so, the scheduler will reset the sleep timer and the app will keep working. It drains the battery in around 1 day though.