I've seen many chains that developed cracks simply from extended outdoor exposure.

But alkali-based cleaners can do the same thing in a matter of perhaps days.

As far as freewheels being consumables, yes, but there are no modern freewheels to fit French-threaded wheel hubs.
The newest of them are perhaps 33 years old!

Thankfully, those Cyclo64 freewheels seem generally robust, with my only concern upon rebuilding mine (in order to shim the bearings a little tighter) was that the lockring/cone might loosen.
So, with my basic wire-loop style Park pin tool, I cleaned the threads and applied Loctite to the threads upon final tightening.

And should the tall, thick teeth on one of these older freewheels develop enough "hook" to cause skipping with a new chain, one can simply put a 1mm bevel up on the driven-side corner of each tooth of the affected sprocket. The previous "failure-to-engage" and resultant slipping is usually remedied this way, for many thousands of additional riding miles.
I do this regularly, in under 5 minutes (and with the freewheel still installed on the bike), using a Dremel with a 3/8"-diameter stone wheel.
I've made the mad dash U-turn back home when riding a new-old bike that immediately showed the skipping problem, and the fix took no longer than it sometimes takes me to find my windbreaker after heading out with one layer too few. I'll then go right back out on the road and make the ride start with still a minute to spare, and with no skipping.

I implore riders not to discard freewheels that have less-common threading and/or desirable mid-range ratios, just because one or two cogs skip under load with a new chain.
They aren't making any more of these!
Shimano UG, Suntour and especially Cyclo w/French threading, these are the best-friction-shifting gems that will only get scarcer and more expensive.