can zenmarket and fromjapan keep your items for x weeks/months and combine them for a single shipping??
fromjapan says that deposits are only valid for 20 days, that's way too short...
https://www.fromjapan.co.jp/en/help/fee#payment_methods
I totally forgot I had an account with Goody-Japan. They do the deposit thing, but it has no time limit, just found out I had 5,000y on it since 2015 and it's still there. They say they keep items up to 60 days which isn't bad.
I'll ask them if they have special treatment for long-time customers about exceeding the deposit. I don't think Japanese make exceptions though