So the (short) life expectancy of of those SWG's is that due to the high heat of the hot tub? The one in my pool is 6 years old and going strong! (man I never should have said that! )All swg cells have a finite life span & will need to be replaced eventually so if your tub comes with one be sure to ask it’s life expectancy in hours & look up the replacement costs/ specs.
Alot of us have the saltron mini / it just hangs over in the tub & is a separate purchase. Some tubs are able to conceal one in the filter area mine cannot as i have a built in floating weir skimmer thing. The cell is easily replaced & costs about $100. My first cell lasted over 2yrs (almost 3). I ordered a new one the same day.
I have never taken my tub’s internals apart to know for sure but the only issue i have ever had was a dab of rust on one of my jet rings - i let my fc get a bit too high for too long in relation to my cya. I corrected the situation & all but a slight speck came off & has never returned. I suspect this would have happened even if there were no salt involved.
I personally wouldn’t want to be without a salt water chlorine generator in my spa or pool. I am prepared to replace the heater sooner if necessary but in general properly maintained water chemistry should help all spas avoid premature corrosion.