A couple of things:
First, two-bath fixing is primarily indicated for fiber-base prints. Although many, including me, use it for film, it is not really economical for film or RC paper unless the throughput is fairly high. Therefore, I assume you are asking your question since you are printing on fiber-base paper and want optimum permanence.
Keep in mind that fixer throughput includes all the test strips and test prints you make as well as the final "keeper" prints. If that total number is less than or equal to 10 8x10 prints per liter of fixer, then you are in fine shape. Note also that the 40 8x10-prints-per-liter recommendation from most manufacturers (I'm referring to the Ilford data sheets here specifically) are for "commercial" or "general-purpose" levels of permanence; for optimum permanence stay at or below 10 8x10 prints per liter for one-bath fixing.
However, unless you are only doing one session a month, it is not really very economical to use just one fixing bath. The life of fixer working solution in tightly-capped full bottles is at least six months. You could easily mix up a couple liters of fix, keep track of the throughput (40 8x10 per liter and then toss bath 1, replace with bath two and mix fresh bath 2) and, over a period of a few months, use more of the fixer capacity. If you print enough, you can keep this going through the seven cycles recommended as maximum and get the most from your fixer while ensuring optimum permanence for your prints. From the Ilford data sheet:
"Ilford Rapid Fix and Hypam working strength solutions should last for up to:-
6 months in full tightly capped bottles
2 months in a tank or dish/tray with a floating lid
1 month in a half full tightly capped bottle.
7 days in an open dish/tray."
Note that two-bath fixing, when used to its maximum, quadruples fixer capacity and ensures optimum permanence.
If you are so cramped for space that you just can't get an extra tray in, you can always do as I do. I separate my workflow into printing and toning sessions. Printing ends with fix 1, wash and dry; toning starts with a soak, fix 2, tone, hypo-clear, wash, dry. If you tone, this might work for your space limitation.
If not, then keep the throughput low and use one-bath fixing. You'll spend more on fix, but maybe it's worth it for you to not have to deal with the extra tray.