Of course the bow should be loosened so it doesn't warp or break, and the violin strings should not be loosened so much that the sound post falls out, but should they be loosened at all for long-term storage?
Some say to store them tuned:
There’s no need to loosen the strings while you’re away
Others say to loosen them:
My understanding is that it's best to loosen the strings -- perhaps not all the way, but at least down about an octave or so -- to reduce tension on the violin. Depending on the quality of the instrument's construction and especially if temperature and humidity conditions are not always ideal, leaving the strings fully tightened can result in the seams at the tail block spreading, letting the tailpiece pull forward and warping the wood of the sides and top at the end button.