Hi Doremus, I assume you do the same when printing with fibre paper?
Roughly the same thing for both film and fiber-base paper: one "session" use of two-bath fixer. In both cases, if I'm developing film or printing over several days, I'll keep the working solution for the next day if the capacity hasn't been reached. For film, that happens less often, since a liter divided into two 500ml baths at film-strength fixes a lot of 4x5 sheets and I rarely have that many to process at once (except after extended road trips, where I might have 100-150 negatives to develop over several days).
For prints, however, I work more slowly. I may only get a total of the equivalent of 10 8x10s per liter done in a day's session (including test strips, etc.). I usually print 11x14-inch prints to start with, but use two liters of fixer per tray, so have two liters of fix one sitting there with a capacity of 36 prints (that's my capacity number based on testing plus a safety factor and, coincidentally, 36 prints is exactly three washer loads). Anyway, it may take me two or three days of printing to reach that 36-print capacity before I replace the fix with fresh.
If you've followed my posts on printing, you'll know that I divide my printing into printing and toning sessions. I use just one tray of fixer (Ilford Rapid Fixer/Hypam) at 1+9 and work till I have 30-36 "keepers." I develop, stop and give fix one, then wash the prints thoroughly at the end of the days session (maybe only 3-5 keepers a day, maybe more on good days). Then I start again the next day, printing. It may take me a few days to get enough "keepers" to warrant a toning session. If my fix reaches capacity during that time, I'll replace it with freshly-mixed fixer.
When I do a toning session, I mix a fresh fix that becomes fix two. Then I soak the prints, give fix two, tone, hypo-clear and wash. If I have more prints to make, the fix two that I just ran 30-36 prints through becomes fix one for the next printing session.
Note that I never keep fixer for more that a few days, well withing the 7-day lifespan of fixer in an open tray (often, I'll bottle it up if I'm going to use it the next day anyway).
Hope that helps,
Doremus