Murakoshi Shinta is a student prone to wild delusions. He has kept this hidden all this while, living his gloomy and mundane life. One day, a tentacled alien parasite takes over his penis. Murakoshi complains to it that he is unable to walk around outside, what with his groin exposed, but the alien assures him that no one will notice as it has the ability to cloud people's minds.

Can you watch too much anime?

People already gave the qualitative answers.
“It’s subjective,” “it’s too much if you think it’s too much,” “of course not, you can’t watch too much unless it’s harming your life”.
Vague, but clear cut that it’s up to your circumstance.
I’m interested in math though. 500 series...
over how many years of watching? A 12 episode series can be burned through in (generously) 4 hours.
100 of those is something like a little over two weeks of straight watching, but assuming you don’t actually watch back to back 24/7 - let’s say, an uptime of 1/4 of your daily hours at the very most - that means you could feasibly watch 100 short series within two months. Five times that amount is less than a year of reasonably intensive daily watching.
Given that, I’d say 500 anime series is really a damned lot of watching… if it was in that time frame.
I’d imagine, at 26, you’ve been watching for well over a decade of your life.
Let’s go with 12 years for a good estimate, since 14 or so is when these shows would take on more than a casual meaning for you. 12 years, 500 shows.
Reasonably, anime can actually span 25 to 60 episodes for mid-length series, and then there are the anomalous long-running 100+ episode ones.
Let’s go with 50 for a more realistic average.
Fifty ~20 minute episodes for 500 shows… almost a solid year (347 days!) of watching.
Split that over 12 years, though, and it’s more like a month’s worth of watching every year. Going by the earlier metric of “spending only a fraction of the day watching”: if in a given day you spend at most, say, 4 hours watching (1/6 of a day, actually less than the earlier number), it would take you… around 174 days per year.
Half a year spent watching pretty casually, every year for 12 years. That does actually seem time consuming, if you assume a pretty homogenous pattern of “4 hours every other day”, or even “2 hours every day”.
But what about binge watching on weekends? If you’re anything like me or others I know who really like watching shows, you’ve spent some free days watching in bulk.
There are around 102 weekends in a year - give that, you’d need to watch… almost 7 hours every Saturday and Sunday for 12 years, on average. Is that still a lot of anime watching? Yeah, it kind of is.
If you do anything else with your free time, it eats up a good chunk.
But is it too much? Statistically, not really - with time management you can fit it in pretty easily, regardless of what else you do.
I will say this, however: watching more than 40 shows a year… you really must have sat through a lot of crap, huh? That’s 10 shows a season, and anyone can tell you there are never 10 good shows a season.
At least, not in recent years.
If there’s ever any reason you watched too much, it’s that.