Never really grows old. It keeps a very consistent quality all the way, even after 16 volumes it's still the same. While the comedy is a bit repetitive, mainly coming from everyone acting weird and the protagonist getting annoyed/weirded out resulting in tsukommis/retorts, it does exactly what it set out to do.
It's a random gag comedy with zero drama, zero story progression and every chapter is merely episodic where the author tries out one situation after another. It never strays from the core concept but at the same time every scene is different even if the retorts often end up being very similar and the characters often acting in a repetitive way. It feels fresh enough to enjoy since the author makes sure to have a new spin/setting every chapter or mini-arc of a few chapters, be it in the school clubroom, the school festival, outside of school, various weird competitions, weird games and so on. What happens is very weird yet at the same time not so out there that you feel like it's impossible. It keeps a sense of very slight realism in that it would certainly be possible that these things happen if you assemble every weird, wacky person around and a straight man or two and then let them do whatever they want.
It's not a masterpiece, but it's an entertaining read and I never felt like I wanted to drop it. While there aren't tons of laugh out loud moments for me, I did smile a lot. Know what you're in for and don't expect any plot, just expect gag-like situations, weird people and people having fun without any significant story progression (don't expect romance either, at best it's about 3-4 girls that appear interested but it's all a joke in the end and they're just used for comedy), it's similar to the simpsons, family guy and various similar long running series in that it's purely episodic and has no real plot, just trying to make the audience laugh, though the similarities end there. 8/10. Will keep on reading it until the author ends the series.