The principle of a keeping a dock or marina clear of ice is to ensure that the natural crushing pressure of ice is not able to squeeze the structure. Ice is so powerful that it can literally lift lake bed pilings out of their footings and toss them about like sticks.
My bubbler works mostly to prevent heaving of our posts during Winnipesaukees spring thaw.
When the lake is cold enough to start freezing I notice ice collars around my posts. These collars are created when ice freezes around posts but the water level drops. I see these collars form lower and lower as the water level drops and the ice settles. This water level drop begins pretty rapidly around January and by mid to late March we are at 'low tide'. The water level drop is not as big a problem as the ice pushes the posts down and will usually break away from the posts not causing damage due to downward forces. Once the ice is at its lowest we enter the danger zone. At this time the ice forms solid around posts. In late March, early April, the ice starts to melt. Rising temps and longer sun light causes snow melt and rain run-off into the lake. Now the water level quickly rises taking with it the ice. If your posts have ice around them the docks will usually heave. It will rip the posts right out of the footings and docks will be damaged, probably not destroyed, but damaged enough to require costly repair.
Your location on the lake will have an effect on how the ice forms and if your docks are in danger. History is a good indicator.
This very short video shows what happens when dock posts have solid ice form around them. Up down, side to side, expansion, contraction...heaved docks.
Bottom line, running a bubbler correctly is a relatively cheap way to protect your docks. It still does nothing when the spring wind sends ice floes your way. Those floes can and will easily destroy your docks. Even the docks that are lifted out are in danger as the ice can crawl right up the banks and damage the lifts.
https://youtu.be/eYN5yfEko6M