engine mount rubber test

Is there a way to test the engine mount rubber. I know it is probably in the "5 year" rubber replacement list. How would I know if they are really needing replacement?

Page 3 and 4 of the following:

https://files.lord.com/pdf/44/PB6304_ProductsForGeneralAviation.pdf

Eccentricity measurement limits (page 4) - I had to call Lord to get the following info: "Mounting Series" number J3049 (table, page 4) is a single isolator, two of which are contained in kit number J-3804-20. J-3804-20 is the part number for a pair of isolators for the RV-10.