Note: this post is based on transistors that were removed from the board tested outside the circuit. When testing transistors in a circuit, surrounding components may/will influence the eventual readings and observations.
Based on my amplifier build adventures from my childhood (I don't work on these any more obviously, so its been a while), building my own SS amplifier with AC187/AC188 pair and using a traditional all germanium design with AC187/AC188 driver and pre-driver stages, AC125, AC126 preamp stages.
You'd not find these observations written anywhere and i have not bothered to go into the technical details, hence please view these as solely based on my practical experiments with germanium transistors.
I had noticed, when the transistor is new (yes, dad got me into the habit of checking these at the shop before buying), we'd get zero resistance between the collector and emitter (in both polarity directions). I had the habit of mixing and matching transistors to observe the difference in performance. Again, i had the habit of testing every transistor with a multimeter before putting them in the circuit.
I noticed that as the germaniums get older, a resistance starts forming between the collector and emitter. My father used to remove these specific transistors from his own experiments and give them to me, for my adventures, saying they have started getting leaky. What i noticed was that the leaky ones that were newer, exhibited higher resistance between the collector and emitter and with older ones, the resistance used to drop (in both polarity directions). I noted that the leaky ones with high resistance in the range of 1k or higher would work normally but as the resistance started to fall, performance issues started creeping in.
Those where times when dad would not let us use 'battery eliminators' so i had a battery box with 6 x AA batteries giving me a 9volt supply to work with. Dad put me on a ration of 2 new batteries every month and I used to rotate my battery stock and survive

. I noticed that when I used output transistors with c-e resistance below 1k, it used to drain my batteries quicker and if the resistance fell below 500 ohms, the output transistors used to get hot while playing and the battery drain increased even more. If the c-e resistance went below 200 ohms, the output volume reduced and distortion started creeping in. I had a design wherein the emitters of the output transistors were directly coupled. Thinking that this was the problem, i introduced the standard 1 ohm resistors between the 2 emitters, with no success. I figured out that my amplifier worked and sounded really good when i had new output transistors with zero c-e resistance. The batteries also used to last much longer.
I had similar experiences with germanium transistors in the pre-driver and driver stages. Leaky pre-driver and driver transistors made biasing very difficult, and my output transistors used to get very hot, despite having thermistor based temperature control. I had problems with distortion as well. This was when the c-e resistance fell below 500 ohms. Again, the battery consumption increased with leaky pre-driver and driver transistors that were leaky. Interestingly the leaky transistors with resistance over 500 ohms seemed to manage ok with a little loss in amplifier gain and a different bias preset setting.
With the preamp stages, using AC125 and AC126, I had issues with low gain and distortion when using transistors with c-e resistance around or below the 500 ohm range. Again the battery consumption was affected but I figured out a way to keep these going for some more time. Essentially what I would do is to play around with the biasing and stabilizing circuit to reach a proper operating point Another key factor was the emitter bias by-pass capacitor. I used to change the value of this capacitor by hit-and-miss to arrive at a nice sounding point. But I would eventually revert back to standard values and just put back my new transistors. Fun times with these adventures.
To answer your question specifically, over time in germanium transistors, i have noticed with c-e resistance to evolve and keep dropping until a point where the c-e resistance is too low (as good as a short) for the transistor to function. That when the transistor is deemed dead. So with your transistors, they may still work but will keep doing down hill (even if not used). Older metal cap germaniums were notorious for getting leaky over time and their casing and legs would get corroded. We could clean the exposed part of the leg from time to time but what happens inside the sealed housing was beyond our control. These are factors that also contributed to the end of the germanium transistor era.
Hope this helps.
Edit: i had some OC71/72 transistors in those times (equivalent of AC127/AC128) and some OC44 ones as well (salvaged from old philips radios). All these eventually became leaky and c-e finally began to short (despite not being in use). I had to throw these away.
