I used to create and abandon decks a lot when I first started. That was back in the days when we had to walk in our bare feet to work, and eat rocks for dinner, and use TTS and transcribe KO2001 by hand. Back before smart.fm or subs2srs. Now I just suspend or delete cards in my oldest, main deck as well as my newer, specialized ones.

I would consolidate my decks and just use tags, but I often forget to tag cards or feel like my computer's taking too long to process items.

I stopped reviewing my KO deck now. My immersion is enough to maintain all that's worth learning from it considering I reviewed it halfway into oblivion I think i'm good.

Definitely wont be deleting my new Vocab deck! But I'm wondering about my KanKen prep deck? I think i'll keep it actually once KanKen is over because I'll be using it again to prep either level 4 or 3 when it comes around 6 months later Plus it's like... the knowledge I gained from doing all the other levels I didn't SRS so some has been forgotten leading to a "well what was the point?" kind of question but i'd say I retained a good portion but I feel a good portion too has slipped. I think i'll keep my Vocab deck and KanKen Prep decks.

My KM2kyuu stuff I've kept too so far because it gives me very little to worry about I usually tend to it every few days and that satisfies it. Because it's the Dict of Grammar deck that I just unsuspended sentences it's wise to keep it around for when I make my way through KM1kyuu but I have an inkling that by the time I come to go through that I may find I've already learned a lot of it through exposure.

I have everything in one deck (or "lesson" for those of you jMemorize users who would get me), so it never becomes obsolete for me - I plan to use it for a lifetime, I even called it Memory Bank.

I'll also keep my decks around forever. I'm a bit disappointed I didn't have anki before, and don't have any decks for those things I learned previously in life. It's rather convenient for picking up things, at the point you left them. When you go through all the due cards with largest interval first, you have a very convenient way of going through it in an order that builds up your knowledge, starting with those things that are easy for you, and let you ease into it again. And I'm sure there is going to be a point in my life, where Japanese won't get as much attention as it used to get and my skill will subside. Just like my skill in French and German did since I hardly get exposed to those languages anymore.

For Japanese I put everything in one deck. But as I go, I do think I'll take some things out of it, like the kanji and vocab decks for jlpt 4 an 3, the Japanese for Busy people deck I started with. But that's just to keep the number of cards down. Most of my Japanese for Busy people and the kanji's for jlpt 4 and 3, already have an interval of a view years. So I hardly get bothered with those anyway.

I don't see why it would come up that a deck should be deleted. You're always adding stuff to it, if you stop adding sentences to a sentence deck, that just means you're done learning the language, so it makes little sense to keep it. I guess some people put everything in different decks (one all about the particle deck, one kanzen master deck, one book A deck, one book B deck) but I think that is making everything harder than it needs to be. Keep a sentence deck and add the sentences you want to learn. You don't graduate from the deck, the cards graduate from it.

Yeah crusade decks have always been kept separate for me. I really don't plan on doing another so now I've just got my vocab deck which I'm keeping forever That any my KanKen prep deck which will be with me until I nail 2kyuu and possibly beyond Plus my grammar reference deck which gives me no trouble.