I always try to renew my domains months in advance, so it's possible I've been missing out on those letters for the last few cycles. I used to get a lot more than that though. It's been a long time, but I seem to remember getting daily junk mail sent to the exact contact info I used on a domain registration and nowhere else. I believe the registrars implemented new policies on whois that helped with that, but again, it's been a decade so my memory is foggy.