What I've done to get around the writing to sd card limitation now is keep my documents in the phone storage and then the less important stuff or static documents on the sd card. I was using dropbox but moved to owncloud last year, either one I just keep the document set I sync pretty small. Other things like the .pdf survival manual you might download I just leave on the sd card since those don't change often I don't bother to sync them.

I just kept the truecrypt volume small since OC doesn't sync chunks like Dropbox. Mine is 100M.