It kind of strange I have had cv boots fail, The rubber can breakup any
time. I replaced the boots on my 84 lasted a couple of years  , German
made , who knows the ones on my 83 mercedes diesel were 20 years old, I
just replaced them a couple of months ago with local auto parts store ones
for less than 100 dollars. The vanagon pass side tranny side boot, I just
replaced right underneath just by dislocating the one side amd letting it
drop down and removing the joint . My point is the rubber can fail in 3 or
4 years or 15 and 20 you should keep at least one extra boot around in my
expierence.  My 2 cents.