I'm not sure if you realize fixers are re-usable until exhausted. They don't really deteriorate by exposure to oxygen like developers and HCA would. I use mine until specified number of films/papers are processed or 6 months. Unless you are doing HUGE volume, it will certainly last longer than few printing sessions.

Also, selenium working solution lasts and lasts. I think I used my 1:40 solution for a year. At which point, the ammonia smell was weak and action was equally weak, so I replaced it.