ZZzZZzZZzz...haha, 5 months! Wow, think you just broke the record of period w/o changing water. Haha. My 1 most was maybe 3 weeks. But well, as long as the LS are all surviving and healthy. I do not see the point in chasing numbers. Oh, 1 LFS told me that his relative does this during water changes.
1. Siphon out old tank water.
2. Connect a hose to your tap.
3. Fill up the tank with TAP WATER!
4. Dump in some salt and taaAaa, its done....
And to think his relative's fishes are actually in pristine condition.
P.S I hereby must make it clear that i do not support this way of doing water changes and regular water changes (the proper way) is highly recommanded.