Paid subscription renewal email timing

[VBFguy]

I have a 3.8.4 board, and the expiration notice prompting renewal for paid subscriptions seems to be sent out a couple days before a members subscription expires

I'd like for that email to be sent out sooner, like maybe a week in advance of expiration, to allow members more time to respond. (some prefer to mail me payment rather than complete transaction through the forum)

I've searched, and haven't found anything that addresses the timing of when this email is sent. Is this possible? I'm guessing it will involve editing a script file somewhere, but I don't know where this might be specified.

Thanks!