Here is the best suggestion I can give you. I don't know where you are location wise, but I'd suggest you buy a lot of Manga or get your hands on some Japanese magazines. I am not an Otaku, but I will tell you why its a good idea.
What i've noticed about SRSing and sentence mining, is that it basically reproduces something that we do all the time: Read sentences.
In a sit down session SRSing random sentences out of context, I find that mixing up "Sentence SRSing" through regular reading is similar. Take the following example.
I watched the anime for Death Note a few years ago. Recently, I bought a few of the Manga, which is actually the first manga I ever purchased. As i started reading slowly through the first book, ( I read with a highlighter), you will notice dozens and dozens of Kanji repeated over and over. Namely, different ways of saying "I" or "we" "there" "that" and so on. But Death Note is a very "adult" manga, and there are tons of Kanji related to "world" "police" "death" "becoming" "belief" "spirituality" etc. I would lookup the meanings of these and then make a note.
What happened is that pretty much all these kanji are repeated throughout the book over and over. As I scanned through sentences, I was doing a sort of "mini-mining" in a MUCH more interesting way. If you see "boku" 僕 one hundred times in twenty pages, its like SRSing for that Kanji repeatedly. It's the same thing with certain sentence patterns.
I am not saying this to say stop sentence mining. I think that canned sentences (if you are going to be reading so many anyways) are good if you are actively using them, writing them and not just remembering the patterns.
Through Manga (or maybe a magazine, whatever) you can sure pick some sentences to mine, but what I find is that a lot of reading of material with similar themes, is a sort of mining in itself. Then when I find some tough beast of a sentence, I might drop that in Anki to really remember.
僕は、世界中で有名になりたい。 (boku wa, sekai chuu de yumena ni naritai) - I want to become world famous.
This is from Death Note, and why I dropped it here, is that its relatively simple I guess. But I didn't even SRS this, I just remembered it as it is, because there are so many sentences about "world", and "becoming" mixed in.
Either way, I feel like i'm rambling, but whenever I read through a lot of these forums, I realize canned systems sort of create context, but I feel that really good context is from these sorts of things, that you can mix with your SRS.
In other words, if you feel like you are going slow, go faster. I live in Japan, and I find that seeing Japanese very often is "SRSing". Skimming through magazines, is "SRSing" in some way, I don't know how well you speak Japanese yet, or are able to read it, but I for one cannot imagine typing so many sentences (initially) when I have hundreds of thousands already printed for me.
Through manga, or maybe children's books, you can find hundreds of sentences that you DONT need to type into anything, but will give you a monster basic vocabulary. What I'm saying is that, you've gone through the effort of learning RTk1, why not work faster?
So children's books, interesting manga, maybe short Japanese articles about the same topics. These are things that you can "mine" without too much typing. If there is a massive sentence you cannot figure out, i'd say mine that. Get me?
I've learned that so many sentences are fragments of others, that sentence mining I only do for evil sentences, which I will barely use anyways until i do my TED presentation here in Japan : p
How's your speaking and listening comprehension? Just curious.
cheers
