It lasts about forever. As always, give the chems a try. If you have issues, try some newer chems.

I have found that much of what we buy from the chem dealers has been sitting around for quite some time already.

I just printed a couple platinum prints last night with the ferric oxalate which is about 18 months old. Worked just fine. Why throw it away unless you can't get it to work?

Good luck!!