How many days do you premix for water changes?

[Vagabond]

Just curious as to everyones practices for mixing their water for water changes .

I do a 10% water change every week to 10 days. My routine is to mix up the change water about 72hrs before, leaving a Mag 1 in the bucket to circulate and make sure all the salt dissolves well. 24hrs before I change the water I throw in an airstone to make sure the water is well oxygenated.

Are there any advantages/benefits of this practice, or are you equally well off by just mixing and changing the same day?