I think, like any language not regularly used...if you don't keep at it, it just fades away. So many people I know that spoke fluently in childhood can no longer do much with it because it wasn't kept up. My hubby, born and raised to age 16 in Germany, can still do a little...he understands a conversation far better than actually speaking it himself. My ex was/is Italian and the same goes for him....he can understand it better than he can in speaking it.
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If we couldn't laugh we would all go insane ~ Jimmy Buffett