In normal conditions, a good holly stick can take 3-7 years to properly season. So on average, 5 years - though I often get away with 3 years, due to temperature, thickness (density), original liquid content (due to time of cutting) and airflow when hung.
But my father, in his 80th year, recently took some hanging holly from his garage to inside his house to work on. Within days it had star shake!!
He hadn't weighed the pieces, monitored them, tested with a digital device ..... just relied on his instinct and experience. This time, that was sadly wrong! It happens :-(
Any dense wood like holly will take a lot longer than hazel etc to season. But getting it 'right' can be a problem! Out of the 60 or 70 sticks I have seasoning, around 10 are holly. There are over 400 varieties of holly and over 200 in the UK. I'm lucky to have certain trees where I know I can harvest superb holly sticks, for fantastic grain. My 'main' stick is beautiful....superb grain, though it was just a white stick when I removed the bark!
My tips: always cut longer than you want: cut all off-shoots about 2-3 inches from the main stem, not close to it: do not rush the seasoning process - it's a dense wood and will take a lot of time to season: if you moved an electrical item from very cold to hot you could easily cause condensation problems.....moving cut wood to a high-change environment can also prove difficult: just give it time & 'cook' slowly, LOL!
For more info of my own experiences please visit
http://www.shootpics.co.uk/beating_sticks.html
Stickler