A common question for people getting into a new dock or lift system is whether they can leave their dock or boat lift in through the winter.  In almost every situation we highly recommend that you take your equipment out of the water to prevent the ice from damaging it.  Ice flows during the winter months and as the ice begins to break up in the spring are the biggest cause of damage to lifts and docks during the winter season if left in.  The wind can push the ice down the lake shore taking your dock or lift with it or bending up the posts or framing.  For a first person perspective watch this video captured on a lake in Minnesota.
The only exception is for people who may be canals, small ponds, or coves that are protected from the high winds and ice flows that can come across the lake.
Just remember "When in doubt, take it out."