I just watched the Star Trek: Voyager episode "Before and After" (Episode 21, Season 3), wherein Kes keeps jumping backwards in time because of some chroniton particles. Is there any reason why she would just jump backwards every now and then, rather than experiencing a continuous backwards flow?
I would offer this suggestion (would prefer it as a comment but cant find that option).
I always assumed/believed that the reason behind Kes's periodic time shift was the periodic decay of the chronometric particles in her body. Radioactive particles decay at a given frequency, so the frequency of decay of chronometric particles could be extremely low. This could resulting in a periodic burst of energy, causing her time jump.
My first initial thought was it was the temperature that was causing the jumps, and their frequency but the body temperature was a side effect of the Chroniton particles.
To answer the question, Kes was in a state of flux, thanks in part to the genius of the doctor who developed a procedure to stop her from aging (biotemporal field) which put her in biotemporal flux. At first the radiation from the Chroniton particles (that were lying dorment in all of voyagers crew, including Kes) were only becoming active again to just make her temporal state flux infrequently, as the procedure from the future progressed it increased the dorment chroniton particles in her body and thus increased the frequency of the jumps.
On a side note, the doctor remedied this by firing Antichroniton particles at Kes and stopped her biotemporal flux.
In 2373, upon learning the Kes had been uncontrollably traveling back in time from the moment of her death, The Doctor and Lieutenant Torres began a procedure to irradiate Kes with a modulated field of antichronitons to purge her system of the chroniton radiation to which she had been exposed in a future time period, and which, in combination with a biotemporal field to which the The Doctor had exposed her in the future, placed her in a state of biotemporal flux, causing her time jumps. Placing Kes in a bio-temporal chamber and initiating the antichroniton field, Kes experienced a series of more time jumps as far back as her own conception, at which point she returned to the present, and was brought back into temporal sync.