If you intend on walking for around half an hour or so then I'd suggest using one, especially now that the tracking isn't working. It does increase the amount of pokemon you see by quite a lot. Plus if you just keep them in your inventory then you don't get ANY benefit from them. Better to use the inefficiently rather than not at all
yeah and it's a big fucking lie about walking around makes more spawn. No matter how far you walk they still spawn every 5 minutes which is bullshit. Since they said they would spawn every minutes if you walked around.