works but doesnt last 30 days

I bought 3 Feliway devices to try to stop the 2 cats from fighting, a behavior that only started recently. It did seem to work after the second refill. I gave it 2 stars because it is supposed to last 30 days. 1 lasted 10 days, 1 lasted 14 days and 1 lasted 26 days. All were in the Feliway brand plug in, 1 was brand new and the other 2 had been used once before. When you need 3 atomizers to stop the behavior, replacing them every 10 days is very, very expensive

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