Question
My mother has a Blue Spruce, appx. 50 feet tall. Leaves have gathered inside the tree over decades and branches with no needles on it have grown.  Should we trim all of them off.

Answer
The dead branches can be pruned off at anytime of the year. Trees will shed internal branches naturally--this is called self pruning. This happens on the branches on the inside of the crown or lower branches. These dead branch can be pruned off as you see fit. Prune them leaving the branch collar and the wound will heal over.