I think like all things, it depends on the quality of the product. There are definitely cheap ferrofluids with mediocre surfactants that break down over time. B

I think like all things, it depends on the quality of the product. There are definitely cheap ferrofluids with mediocre surfactants that break down over time. But I also suspect (never looked, just inferring from the myriad of surfactants out there) that some formulations exist with way longer lifespans.