I performed a detailed analysis of Yeti kills statistics to answer this question. I used archival stats provided by Tibiabosses. I checked stats from 2019/2020 of about 20 highly populated servers where the possibility that the boss has been missed is the lowest. The event takes place between 01-Apr and 01-May, so I mostly focused on this exact time frame.
Please take a look at the screenshot below. It shows the situation which occurred on Astera, in 2020:
Yeti usually respawns on Folda between every 19-25 days.
We can safely assume that Yeti seen on 2020-03-31 was on Folda, as the event was not active yet. The second entry must be Chyllfroest then because the required amount of time from the aforementioned kill didn't pass yet.
Let's move further in time to notice that Yeti was spotted on 2020-04-22 and 2020-04-23 (I wrote "probably" up there because we cannot determine the exact location of these two). What does it mean? Well, this is our answer. We have 4 cases where Yeti has been spotted over the course of one month and they follow the pattern which we know from Folda.
The final answer is: Yeti can be found 1 or 2 times on Chyllfroest during the whole event. The mechanics work exactly the same as on Folda.
This knowledge can be particularly useful to determine how often you have to check the Chyllfroest spot. Just cleverly analyse the stats on your server and you will (most of the times) be able to predict not only when the Yeti can spawn, but also where!
Finally, please find one more example of 4 Yeti occurrences during April - this time on Kalibra:
Source: https://www.tibiabosses.com/history/