From what I could derive from
this thread, someone reported to put all pics, video's, music, maps, documents, etc...on the SD card.
Apparently that prevents (mostly) the Other storage to grow out of proportion.
When I got GDR2 my other storage was at 475mb, I have since gotten GDR3/black and since 2 my other storage never gets past 500mb. It will rise up to 495mb and then goes back down to around 450mb. Rises up to around 500 and then goes back down again. Don't know if it made a difference; but I added a 64GB SD card to my 820 and all pics; videos, music and maps goes to the SD card. Still have over 55GB left on the SD card. Other storage has not been a problem and I don't really think I ever had a problem with it. Things will be nice if 8.1 allows putting apps on the SD card. IF that happens I probably won't upgrade for awhile. I like the 820; and think its the most underated phone in t he Lumia line. Same guts as the 9XX series; but smaller and with a removeable battery, and a SD card Slot. The upgrades has made it even better.
Don't know if it's truly solid, but I also have just about everything stored on SD, and I must say I also never once have had an issue with other storage...