Verifying Value is Not Equal Before Assigning Value

Is there any point checking to see if a value has already been assigned to a variable or is it better to just simply assign the value? For example, if X is going to equal 1, is there any point checking to see if X already equals 1? Example code below:

if X != 1 {
    X = 1
}

I ask this question become I'm looping through a bunch of children sprites and changing the alpha values to 0, which most are already set at 0. So I'm seeing if there is any benefit in checking the children's alpha value first (I can't see the benefit).

parent.enumerateChildNodes(withName: "*", using: {
    node, stop in

    // if node.alpha != 0 {

    node.alpha = 0

    // }

})