Same for me. I’ve posted both in Swedish, English and Japanese in some posts, since I just…feel like that makes more sense to me. I just can’t connect to the English names of plants in the same way, as names I’ve learn years ago, sometimes from ages ago when growing up. ^^
This is perfectly normal. For any language acquisition, you’ll just have to make the rounds and slowly learn new words in different fields. I’m not doing anything focused, not really. Not even in the thread I started
I would need to make anki cards or something to actually learn all the fish names I’ve posted in the thread. now, it’s more like an extended encyclopedia with pictures and Japanese - English translation posted. XD which is fine really. Until I have actual need to know these things by heart, I just don’t have to learn them. It’s fun too look stuff up though, so that’s enough of a reward I feel for now. 
I think it probably will. Why one stops doing something can be complicated, and have multiple reasons, but I feel like I would not have gone as far with Japanese, unless I were reading, listening, watching, gaming things I love in Japanese. They’re both the learning goal, the carrot and the challenge - all wrapped into the same experience really. 