Well
I bought J24 # 2733 new in late 1981 and #2930 used in about 2008
The J24 and J30 were early boats and the first big sellers the core issues are well know
The J24 was there first boat and first of the MANY keel issue and other quality issues with the at least the first 1800 something J24s having a vermiculite keel sump that waterlogged and had to be refit and the J109 was the most recent that had much keel repair
remember they design the boats they do NOT build them this is subcontracted out to many places with TPI being most likely for that time
I still like the boats and if money and lifespan were no object would buy a third BUT there NOT gonna be in the old boat haul of fame because there is only 1/8" of glass between the balsa and the water
Also look into the J44 class as there very open about the service life issues and the refits necessary to keep the boats safe
It is very big class here with more than 7 active boats on LIS