Nice try Canon - it seems that you still want me to loan you my money (interest free!) for an unspecified period of time.
Is that worse than just giving it to them, permanently?
I liked the instant rebates... but last year there were some deals to be had on a 24-70 f/2.8 mkii and a 100L that were made sweeter by the mail in rebates.
I'm not a huge fan of mail in rebates... but if it affords me the opportunity to save an extra $50... I'll do it.
But you don't save $50 - it is less than that.
For example, if you buy and have to pay sales tax, you pay sales tax on the amount prior to the rebate being deducted. You don't ever get the extra tax paid back. Second, you need to spend time, effort and supply your own resources (envelope, stamp) to post the rebate. You may even need to drive somewhere just to buy the envelope + stamp, so add in the cost of gas to get that. Third, if your credit card isn't at $0 balance every month then you pay interest on the pre-rebate amount. Fourth, if you've got enough money in a bank account for it to earn interest then you lose the extra interest on the rebate total.
Individually, they're not significant, but they can easily add up to be a couple of dollars or more.