"A foolish consistency is the hobgoblin of little minds, adored by little statesmen and philosophers and divines" - Ralph Waldo Emerson
Folks approach this kind of decision (or the decision to brush one's teeth, or wear a seatbelt) in various ways. Paul may have a "Paulicy" of never wasting anything, and separates them; doesn't-give-a-damn Sam would never bother; Sometimes Suzie separates them when she has time, and doesn't when she's in a hurry.
The decision hinges on the value of a filter in terms of cost, waste, etc. The value of a single filter is a rounding error, but clearly a lifetime of wasting filters can add up to a lot of filters magnified by the number of people wasting them. Why not go to great lengths to save every filter possible?
In this kind of situation, a rational agent may decide to institute a policy of doing things in a certain way, but accept deviation from that policy under special circumstances. My favorite example of this situation is in medicine with central lines. A left-sided line is not supposed to come at a 45-degree angle to the wall of the SVC; rare cases are reported where, over time, it can erode through the great veins and cause fatal hemorrhagic mediastinum. But what is the probability of that? Something on the order of one instance per 10,000 lines. Supposing you have just placed a left internal jugular hemodialysis catheter and the tip is at the proscribed 45-degree angle. You can't retract that catheter, and you can't advance it either. Do you replace it with a longer one? What if your right internal jugular 20 cm catheter is "too deep" into the right atrium; do you retract it and use the little clamp, knowing that often the line slides in it, increasing risk for infection? What if the upper great veins are suboptimal targets, but you've read the Parienti paper in NEJM and know that the risk of infectious and thrombotic complications doubles (but increases only a percent or so, absolute) with femoral vein catheters? Should the femoral vein be verboten?
In cases such as this and many more analogous ones, a rational agent may employ a general policy of always trying a priori to avoid the 45-degree angle; select the appropriate length catheter; and favor the upper access sites, but to allow exceptions whenever the probability of an untoward outcome in an individual case is low, and the costs of avoiding it are higher. In the case of the 45-degree dialysis catheter, the risks of infectious and mechanical complications of repositioning or replacing it exceed the benefits, especially if it is going to be in place for a short period of time. Reluctance to use the femoral site which has but a 1% increase in adverse events compared to the jugular can lead to far greater complications from forcing patients to lie flat for prolonged periods, or from failed attempts under more difficult operating conditions with non-collaborator patients (delirious, thrashing). The policy to default to a preferred standard becomes irrational when, in a specific case the preferred standard doesn't deserve its status.
The same situation is true with many policies. Studies have shown that a policy of routine use of right heart catheters in sepsis or ARDS does not benefit patients (it also does little harm). So, we have policy of NOT doing routine Swan-Ganz catheters. But that hardly means that in specific circumstances we should not do them. The same holds true for so much of what we do in medicine. Part of the problem is that physicians memorize the policy and the direction of harm/benefit ("there's an increased risk of DVT with femoral lines!"), but they don't know the magnitude of the effect.
So, to be a rational agent, you should establish a policy of what is best, under optimal conditions, for all-comers. But when you have more information a posteriori (because the line went into the wrong place; or you forgot your helmet; or your kid fell asleep in the car seat), default to the policy only if a cost-benefit analysis justifies it. Also, be on the lookout for situations where the all-comer policy does not apply. Like the 90-year-old patient with a small (250cc) complicated parapneumonic effusion. Policy says drain. Rational practice says hold tight; it's a small target, risk of complication or failed drainage higher, benefits of avoiding a small fibrothorax (losing 250cc of vital capacity) in someone with reduced life expectancy and limited mobility are small.
I was not in a hurry, so I separated the filters. Had I been running late or the kids were screaming, I may not have.
Edit to add later in the day: it occurred to me that I do a lot of anal-retentive things in my home, many concerned for the environment or recycling. Example: we don't use paper towels, or disposable plates/silverware.
The consequence is when we have a get-together, guests can be out of sorts with my "environmental policies." Even though our family, as a routine policy, is (I hope) happy to adapt to these well-intentioned standards, the social costs of this routine policy are off-putting to my guests. So, I keep things in perspective: this is just one gathering, a roll of paper towels here and there is no big deal to avoid the off-putting social costs. So we use disposable stuff on occasion when the convenience in a specific instance overrides the general routine policy goals. Same would be true if you had a general policy of "no shoes in the house" that you let lapse when you invited guests into your home.
Many doctors would do well to make such exceptions to their general policies, in the name of building (or not spending) "social capital."
