I think FX-39 keeps quite well. So there are two threads on Photrio about the lifespan of FX-39, and I have some Adox FX-39 which was made in mid 2016, and I have just done a clip test of frames from -3EV to +3EV like Blakemore would suggest, of a white towel. To my eye, its done a great job. I've also just done the same with some Compard R09, made in 2022, and its also been absolutely fine. I've not been storing these particularly well, they have been in my garage, which is not heated. Both developers were unopened. I guess with more exposure to oxygen, the results could have been different.