I think I’m going to give a bit of a different opinion, but I think lessons have been getting continually harder, generally speaking. I think this is mostly because in the first 10 levels all of the kanji you learn have basic meanings for the most part and are also quite common so there’s plenty of reinforcement. The primary problem I’ve faced with the later levels however is the increasingly complex/obscure meanings. Readings, as other people have mentioned, most definitely get easier because you begin to recognize phonetic components.
Just looking back at my past level, you can see how remembering 騒 (boisterous) or 延 (prolong) would be harder than something like 服 or 新.
Summer holiday hit after level 10. So no, it didn’t get easier. It got harder actually.
But that was mostly due to personal circumstances.
I also knew a lot already from the first 10 levels. The further I get, the less I know. I’m entering the unknown. And I have 70 lessons pending, so i’m going to chop off 10 of them now.
The same as most around here: it gets harder. It feels like taking that cough medicine: you know you hate it but it will help you in the long run in your language acquiring process.
I’ve just gotten to level 10. Koichi is still telling me it will get easier, but this time he provides an explanation.
It means you finished the hardest group of levels, which (for most people) is levels 5-9.
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Level 10 is about where things begin to even out. As in, you should be burning items and getting them out of your review queue.