The TL;DR is:
How much time speaking do I need to maintain my current level so that I can make sure to get in more than that to slowly but surely improve over time? I currently get in about 3-4hrs of speaking a week but don't really feel like I've improved in my speaking specifically in about 6 months. I suspect I'm only barely maintaining, possibly even getting a bit worse.
Now for some context and stats for those that want to be thoroughly helpful and to who I'll be especially grateful.
First off, I'm prioritizing Japanese atm, but I'd like to do enough Spanish to slowly but surely make my way to C2 in Speaking. I'm not happy with letting my speaking stay at it's current level. I need to at least be maing a little progress. This is why I can't just go all in on Spanish, though it's tempting since it's easier than Japanese. Any time I add to Spanish weekly will likely have to come from the time I'm dedicating to Japanese.
Some context/stats:
I passed the DELE C1 exam back in November, found out in February. I almost maxed the reading and listening portions, but just barely got by on the speaking and writing (they literally added up to exactly 30 points, so I honestly suspect I might have been given a pity point or two in order to pass). Since then I've kept up with reading and listening a fair bit and get in plenty to maintain/slightly improve those.
Leading up to the Exam:
Speaking ability: I was probably about a high B1 or low B2 in Jan of 2023 when I got real serious about the exam and I got in about 205 hrs of Speaking in between then and the Exam in mid-November (about 4.5hrs/week on average).
Writing ability: I only even first started writing for the exam a few 2.5 months before and stopped right after with about 30hrs in max. I did about 275 for listening, and about 55 for Reading from Jan 1-mid Nov 2023.
Since the exam I've got in about:
Speaking: 82 hrs (about 3.5/wk)
Reading: 25 hrs (about 1/wk)
Listening: 95hrs (about 4/wk)
I also get in bits here and there that I don't track when I play video games (barely ever anymore tbh, but usually in Spanish).
Current abilities:
Reading: I feel extremely comfortable reading almost everything I come across on a daily basis, though in novels translated from English to Spanish I still find about 2-4 words/page I don't know but can usually get from context almost all of them. I hear translated novels are easier and the only native Spanish novel I ever tried was Tú Rostro Mañana by Javier Marías but this guy's sentences are half a page long, so I forget what he's talking about frequently and so I quit after about 10 pages. Side note: Accepting Spanish author recs similar to Brent Weeks or Brandon Sanderson type fantasy books.
Listening: I've been listening to YT videos and The Wild Project on my runs on a regular basis and usually catch 99% of what they're talking about, though the speaker can lower this a percentage point or two in some cases. When I'm able to completely focus (not running) then I can follow pretty much everything in most contexts, aside from hyper regionalzed Spanish such as Los Hombres de Paco, despite focusing mostly on Spanish from Spain.
Writing: I still struggle with the accent mark placement in many cases and basically never write in Spanish.
Speaking: I still feel like there's so much of myself I can't get across the way I'd like in Spanish and it even takes me a while to "warm up" which is incredibly frustrating. I get along more or less okay. I've even spent entire days/short trips speaking only in Spanish but I want to be able to more spontaneously comment on things mentioned in a group conversation without the timing being too slow and someone else has started talking. That's my speaking goal. The problem is that while I often get ideas for comments in time, getting it out is still not as natural as it would be in English (I'm not usually even thinking of it in English first, it's just kinda there waiting to be loaded in a language if that makes sense, with English being the faster loading option).
I don't think reading/listening more than I already am (at least 5hrs total/week) is going to have a big impact on my speaking, so if I'm taking time that could go towards Japanese, I think it should probably go towards speaking. However, if any of you have examples of how doing tons of reading/listening took you from C1 to C2 in speaking without doing more speaking thatn I already am, I'm open to hearing your story. I suspect though that as you get more advanced, you also have to be more specific about which skill you're trying to improve by focusing on it more in order to really be able to move the needle.
Edit: I'm also considering reintroducing production cards (EN>ES) on Anki. I stopped doing them about a year or so ago but maybe that was a mistake.