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You see this (or used to, anyway) from time to time with gas strikes.
If it’s just a month of “don’t buy,” it wouldn’t do much in the long run. All that does is time-shift demand to when the strike is over. If the company can anticipate well enough, they’d raise prices when the demand comes back and come out ahead in the long run.
You have to use/consume less, and for an extended time period, not just change when that purchase happens.
But yes, with that caveat, use less, and choose the lesser evil when you do need to buy something. The individual effect is small, but small things add up.
Practical Engineering?