In a spa that is used regularly, an ozonator can have benefits, helping to oxidize some bather waste but with slower kill times than chlorine itself. In an infrequently used spa, it will slowly breakdown some of your FC whenever it runs. In a bromine spa, an ozonator can help oxidize bromide back into bromine so it is a better fit for bromine spas overall.
If you're using the spa often, I would leave the ozonator connected but try to set your pump to run after you've used it, but minimal run time when the spa is not in use to reduce the ozonator consuming some of your FC when bather waste is not present. Most ozonators run whenever the pump is running so that's the only way to control the ozonator run time. If you're only using the spa a couple times per week, I would disconnect the ozonator.
This also got me wondering, has anyone ever put a DIY or aftermarket switch on the ozonator power cable so that you could manually turn the ozonator on or off? Might be interesting... and difficult.