Selling an LP collection of jazz in Northern California

I think the OP wants to sell the collection en bloc. In that case one cannot expect to receive catalog value for each individual LP. That can only happen if you sell one LP at a time, which is very tedious and sometimes contentious. And time consuming.

sounds like many of the reasons the OP may have migrated across to a Source that is Digital.

Recent knowledge discovered suggests Digital Source can be acquired for the price of Cantilever / Stylus to be used on a Phono Cartridge, with such info being available, Digital once more shows it has great VFM.

Over the past few years, on more than one occasion, I have been successful at purchasing near 100 CD's for the value of which one Typical Price for a New Purchase Vinyl LP. CD's in use have extended the life of my Stylus in a way that was not imaginable.     .    

Yes, not playing LPs makes your cartridge last a lot longer.  Stylus and cantilever will last forever, if you sell all your LPs and listen only to CDs or streaming digital.  But then the cartridge itself will deteriorate anyway just sitting there. Great idea.

The Cart' is deteriorating from the day it leaves the Factory, or possibly whilst a Single Part whilst stored at the manufacturer's. Especially where a Damper Part is the concern. 

Playing a Cart' infrequently over a long period can maintain the original parts used for the build, but the idea using a Cart' assures improved condition over a same model stored Cart', will be very very difficult to prove, what is best for the Cart's function.

My experiences are that those interested in Vinyl as the Source, are not limited in their Cart's at hand, Cart's out of production for more than 40 years will be found in collections readily available to be used and kept alongside Cart's from much more recent production periods. To owners of such Cart' Collections, such a option for experiencing Cart's will be viewed as more than a 'Great Idea'. 

I am in this Camp of Cart' collectors, and have no time line as to when a Cart' is no longer worthwhile acquiring. 

Any Cart' is worth owning, if it is of interest. Third  Party Services, do Great Work at restoring these Cart's to perfectly functioning designs. I have a Cart' used as my most preferred, as a result of a design used by a Third Party Service.

I do not know a age for a Cart' to strongly suggest it should be avoided. 

I am surprised to learn that your attitude is as stated, because many of your posts are about cartridge deterioration either due to use or simply longevity. In any case, I agree with your sentiments as stated above. I’ll take it a step further by saying I far prefer among used cartridges a sample that does not require a rebuild as is. This is because I think some methods and materials for construction may no longer be available even for skilled rebuilders. For example, OEM B&O cartridges have a sapphire hollow tube cantilever, which reduces mass . Rebuilders will use a solid sapphire cantilever that loses some of the delicacy of the original sonics.