you should drain and fill your hot tub every 3 months your TDS (total dissolved solids) levels should never go above 2000ppm it takes way more Chemicals to sanitize it properly, it is true any tub can go 6-7 months between draining but it's going to cost you way more money in chemicals..
Sundance is owned by Jacuzzi and in my opinion Sundance is a way better tub.
hope this helps