I.E. a 1.5' has an operating capacity of 45K If you set teh salt dose at 15lbs/cuft and what you use is subtracted from that and when you regenerate what you used, you're back to 45K.
Guests use gallons off the meter but then if you use the variable reserve feature you don't need to worry that guests will cause an overrun of the reserve gallons.
And don't lie to a softener control valve unless it is the time of day you're lying about. And with a Clack and all other electronic controls, there is no need for that.
Most if not all resin manufacturers suggest a weekly regeneration for residential softeners.
You may be using 64 gals/day now and only 3-04 gpm but that gpm is way low from my experience, but a 1.5 cuft is not capable of treating near the max gpm water a 3.5 bathroom house can use if you start using a large tub or shower. AN you can 'cuz Dad moves in with his new sweetheart or Mom with her new boy toy move in. Or you have twins...
BTW, a shower is 2.5 gpm, a washing machine clothes or dishes, 3-4 gpm each and a toilet 1.5 or so. And guests use more fixtures than you two will being there alone. The efficiency of the washer has nothing to do with it's max fill rate gpm, they just shut off the water sooner than a less efficient washer does which equates to fewer gallons used, they still fill at the same 3-4 gpm rate. The connection hoses and plumbing feeding them and the water pressure is the same right? Sinks are 2.2-2.5 gpm.
Channeling is a potential problem if the unit doesn't regenerate frequently enough.