by properly processed, I mean completely fixed and then well washed.
This is the crucial issue. The gold isn't so much an issue; in chemical terms, it should be stable enough to last a century on display in a typical living room. Assuming that the toning is taken to completion; i.e. most of the silver has been replaced by gold.
The problem with gold-toned salt prints, and also untoned salt prints, is the difficulty of removing all traces of unreacted silver halide from the paper as well as the silver complexes that emerge during fixes. Due to the nature of the paper we use, which is a very open structure to which particles adhere readily (as opposed to baryta or even PE paper used for regular darkroom printing), it's very, very difficult to wash a salt print well. Sometimes it even proves to be practically impossible!
The result is that yellowing/browning of the highlights and white borders of the print. This process is accelerated by UV light and by heat, so it can be slowed down by storing the prints in the dark, but it cannot be stopped by practical means nor can it be reverted.
In my experience, it's particularly difficult to cleanly wash salt prints that are gold-toned
before fixing; interestingly, prints toned with gold
after fixing wash much more easily. The downside is that gold toning IMO works especially well (fast, to completion, with beautiful blue/blacks) when done before fixing.
To verify the quality of your processing, I recommend the following:
1: Always print with a masked border that ensures you have an area on the paper that is sensitized, but completely unexposed. This will help you see if your whites clear properly - and
remain clear in due course! Furthermore, it helps to have a masked area adjacent to an unsensitized area of the paper so you can see the difference between the pure paper and the paper that has had silver sensitizer applied to it.
2: Make a test print and 'torture' it - feel free to dry it by applying a clothes iron to it at its highest heat setting (there's no gelatin layer to be worried about anyway!), put it next to a south-facing window, etc. Verify if the masked borders remain clear. There's about a 99% guarantee that you will see at least
some discoloration in this border compared to the pure (unsensitized) paper. The degree how badly it discolors is an indicator of the quality of your processing.
I feel salt prints, even if they are toned, may not be ideal to be hung in one's living room.
Be that as it may, given the story above, consider that if you enjoy making them, and if you like the end result, there's no reason to abstain from adorning your living quarters with these prints! If in 10 years' time they have discolored so badly that you no longer like the prints...make some new ones