Do dogs bite their tongues?

    What is better serial or parallel use?
        In other words, when you use something that will eventuall wear out, which will last longer, using several copies of this item serially or in parallel? For example, shoes, toothbrushes, cloths and other durable items that eventaully wear may last longer if you alternate between several copies of the same product. What if you had three pairs of shoes and each week you wore a different pair for three weeks? Will the three pairs last longer, the same or shorter than if you used each pair until it wore out and was no longer useable (in your opinion)? How about a shirt, a coat, manual and electric toothbrushes, electric shavers, razor blades or you name it? Cloths can be alternated around laundry cycles, toothbrushes around brushing routines

        I wonder if any consumer organizarion, any product-manufacturer or any technology center ever studied this question. After all, the answer is directly effected from the properties of the materials from which the product is made. And some material fatigue slower if they are given "rest" time, time in which the initial properties can be restored by virtue of natural forces such as gravity, flexibiity, chemical reactions, tension (e.g., within fiber), etc.

        If you know the answer, you can save money by smartly using duplicate copies. For items that wear longer in parallel, it is better to purchase a few at the same time, even if prices did not tend to increase due to inflation, and use them in parallel. On the other hand, it is better to purchase products that wear better when used sequentially one at a time, as their price may fall or you may get tired of them and stop using them.
 
 

   Question I have about math