My premium time expires in a week, and I've received e-mail warnings for the first time today. I've received a total of 16 e-mails so far to remind me of this within the course of one day. The first was sent today at 16:04, the last one at 22:18. I figure there may still be more but right now it's been 16.
Not sure if this is a bug since I rarely let my premium get close to expiring but I figure it probably shouldn't be spammed this much.
Here are my details: