I bought my 1976 NC34 mk1 ZARZUELA some 21 years ago. On taking delivery I noticed that the stays were slack, fore cabin door hard to shut and an obvious sag in the lintel. None of these problems had been mentioned by the surveyor who had passed the rigging as sound.
On lifting the deck around the mast step we were horrified to find that the cross beams were spongy due to being soaked for years because the deck air vents had never been opened to allow any moisture to dry out. Subsequently I only shut the vents when going to sea and re-open them whenever in a berth.