We have a 300 gal. above ground spa that I maintain with bromine. In 2014, having followed the thread here on using/starting up a spa with a bromide bank, shocking it weekly with chlorine and after usage, and doing my best to maintain the water chem, the water is still clear. Sure, after running the jets on high, it takes slightly longer for the water to go clear vs. from when the water was fresh, but it still clears regardless. But, I do know that with a smaller body of heated 100+ degree water that it was recommended to drain/refill every 3-4 months, if I recall correctly. Is that really necessary? Or, is that just a general guideline based on spas that see frequent usage?
I am a conservationist, but a realist as well. I don't want to waste water, but will replace it if necessary. Just thought I would post this to get others opinions. FWIW, we don't frequently use the spa. I am pretty much the only one who uses it regularly, and at that it is about 1x (maybe 2x) per week. I know the spas usage will change when our kids are older.