I've been doing Menards merchandise-check rebates for many years. And I mean, a LOT of them. I would say on average, I submit about two each month.
97% of the time, I've had zero issues getting my checks. In fact, I'd say their clearinghouse, Rebates International, is the quickest and most reliable rebate processor that I've ever used. It's rare that you don't get your check in 3-5 weeks from when you mailed it in.
And, on the rare occasion that things don't go as planned, you can just email them to explain. They'll email you back and you can then reply by attaching a copy of your submission materials (you DID keep a copy, didn't you?). Assuming you actually met the submission requirements, they will fix it within 10 business days. I've done this a handful of times, and always found them to be fast, courteous and honest.
Something else to consider is that, if you sent in multiple rebates, the rebate checks aren't always grouped as you might think they would be, but you will still get your rebates at some point. I've had multiple-rebate submissions (sent in one envelope) that arrived on separate checks. I've also sent in separate rebates in separate envelopes, that were subsequently consolidated onto one check. In and of itself, it doesn't seem to mean anything.
Other times rebates have arrived just fine, even though they didn't show up on the website (although this is also rare). So if this happens to you, don't let that bother you too much. You'll probably still get paid, and if not, your submission probably got lost on its way to them. Just contact customer service and be prepared to send them a copy of the submission. They'll get you fixed right up.
Their rebate CS contact page is here:
Product or Service Mentioned: Menards Rebate.
Reason of review: Good customer service.
Menards Pros: Convenience, Price, Rebate program.