You probably should call the manufacturer and ask them, or look in the owner's manual and see what it says.
Gee, I've read that membranes are pretty sensitive to chemicals????????????????SK told me to just pump in potable antifreeze.
Call your manufacturer
5 years ago I bought a boat with a "pickled" membrane and -100 propylene glycol in the pump, ETD, and lines. Based on the conventional wisdom I'd heard similar to the above I assumed I'd need to replace the membrane after 5 years of it just laying horizontally in my basement, only occasionally being rolled over or even moved. But just to see if all the connections were ok and the pump and ETD worked I started it up with the old membrane and it's been working just fine for about 2 months now. Salinity monitor OK's the product water within about 2 seconds and it tastes fine and system is producing at its rated output. Maybe I just got very lucky but I think my experience illustrates that the 6month/1 year guidance is quite conservative and your pickled membrane may remain usable for a much longer time than these estimates.Use SC-1 in spectra. Takes up no room so carry four. Also you can't find RV antifreeze once you're in places where's there's no risk of freezing in winter. Takes less then 15 m to do. When in the states 100 RV antifreeze is available and cheaper than SC-1 so use that. The SC-1 is good for 6 m. The 100 RV stuff is good for a year