There are no reaction wheels on Voyager [...] Voyager is not spin-stabilized. It used thrusters for stabilization, to provide a stationary platform for the cameras.
In this scenario, the last straw would be the hydrazine freezing which leads to loss of the thrusters.
There is enough hydrazine to last beyond the end of the mission, about 25% of total tank volume is still available. From Descanso volume 4, you can see enough hydrazine for attitude control is available to last until 2040/2048
[...]I have found no references to spin stabilization as an option for Voyager operations: because of the above, the Voyager team never had to consider spin stabilization.
The Voyagers have a rather unique situation; after decades in deep space they are still able to perform accurate acceleration measurements via rate-range data from their coherent transponders, and so there was an effort to pay careful attention to their thrusters so as not to interfere with radial velocity measurements.
- How are the Voyagers' thrusters configured in a novel way to minimize accelerations along Earth-spacecraft axis?
- How are Voyager's 16 thrusters oriented?
- How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?
- What does it mean when the Voyagers "switch thrusters"?
Question: How much do the Voyagers' attitude drift over time? How often are its thrusters used for attitude control? Are the valves actuating and thrusters burning once an hour? Once a day? Once a month? Are they both about the same?