I recall the problem of thread coming unwound being brought up awhile back. What I did also keeps the thread from getting dusty if you store it on a thread bed. As soon as I can get the hubster to make me a large thread bed, that's where mine are going to go.
I purchased 2" x 3" plastic bags (100 for $1.99) and 3" x 4" (100 for $2.47) at Hobby Lobby and put them around the threads. The bags are found in the jewelry making section. Works great - no more unraveling. If a little bit of thread comes loose when I put the spool in the bag, I just turn the spool until the thread re-winds. Comes in handy when I take the thread with me somewhere.
Hope this helps someone.