One of the first things that happens to me over the winter is that the swing plane goes a little and there are many reasons for this and really you could call it the whole swing. The problem with this is that what causes plane faults differ from person to person. Apart from your usual exercises you still need to practice the full swing and rather than smashing a few lightbulbs, it's really worth the effort to visit the range ... and if you can get your pro from the armchair by the fire, so much the better.