Deep sand cubicles and replacing sand.

[kill]

For those with deep sand cubicles do you ever dig out the sand and replace the back half of the sand bed ?
If so how often?
Mines done 2 winters and the odd cubicle has a solid compacted lump around where the cows udder rests which is only shown really if sand starts getting a little low so would this be the time to replace?
Sands always raked twice a day and topped up regularly