Hi Rojo! Typically speaking, if you treat your speakers right, the ferrofluid doesn't need to be changed at any specific time or on any set schedule. However, if you are changing the coil/diaphragm assembly or you find that the fluid has congealed and the motion is getting sluggish, you need to get the old stuff out of there. Fluids manufactured many years ago are not in the same league with the fluids made these days. They didn't have the temperature stability or the length of "gel time" we see now. It's fairly easy to clean out the old fluid once the coil is out of the way, but all too often the manufacturers that DO provide replacement assemblies won't provide a fluid packet. I think their effort is to get you to do the refurb and then say "Man, these things just don't sound like they used to! Time for new speakers!". There are also some sources out there that sell fluid packets for ridiculous prices. They will remain nameless, but I do know one source that is great for these "retrofit kits". That is Parts Express. They have a number of different sizes of packets for the different sizes of drivers, and you just let the magnet drag the fluid out of the tube, no fuss, no mess. It's a general purpose ferrofluid they sell, so it will do a pretty good job with most drivers on the market. If you have special needs it is a good idea to ask for special help, but you can get that by sending an email message to the info@ site for Ferrotec Corporation where you will get fast assistance.