I get the question all the time. Should I drain and winterize my spa or let run and just turn down the temp? Good question. Either one is exceptable as you go into the cold months of winter. By leaving the spa run and just turning down the temp. The spa motor and heaters have a chance to heat and turn a couple times a day. With this it will drive up cost some on your electric bill. Along with the cost of paying someone to add chemicals every other week so not to turn green and get a spa disse. This also allows you to know the spa is good to go when ever you or your famliy decide to pop in for the weekend. And all you need to do is turn up the temp and your hot tubbing.
By pulling the plug and draining the lines you by pass those costs. But the spa sits idle for months at a time. This is after running full bore all season long. We tend to find more mechanical damage with this method. One the spa motor sits for long periods of time the salt likes to corrode the motor shafts. We also find once it begins to run after a long periods of no use the motor seals being to leak. These repairs can surpass the maintenance costs by far of keeping the spa running and serviced all winter long.
So by leaving your spa run all wointer and paying your pool and spa service to do a bi-weekly service is the way I suggest. But you can always go for the crap shoot of completely shutting down for the winter. How ever NEVER just pull power and leave full of water till the next time you come down. I promise you will be calling us with a manifold that looks like this.