How long can you keep transfer dyes, once they have been made up into solution? Well... the answer seems to be, indefinitely. Providing, that is, that you keep them in a jar, preferably in a cool place. I have even found that, if you let the dye dry out, you can add more water and redissolve the remains...but I think that's taking economy a little far!! I keep my dye solutions in coffee jars (we drink rather a lot of coffee around here...).
The image is of a transfer dyed quilt entitled 'It's Coming To Get You!'.