In the 5-month span, I got maybe 1 email a month or every 10 days from them. That is what I call reasonable; one even went on to give mailing list me real information about marketing without trying to sell me anything. So the question, how can you abuse your mailing list? By taking advantage of the subscriber and the ability to email at will, use it sparingly and you will most definitely see better results. Why: Why do people abuse their mailing lists?
Well I would love to say it is because they are new and ignorant, however I tested 20 well-known marketers and 98% of them abused their list. Therefore, the question begs to be answered, why. I believe there is this false idea on the web mailing list that if you shove something down a person's throat enough, eventually they will accept it. The reason I believe this to be false is that, through the Internet, people are becoming more aware of such tactics and thus becoming immune to their abilities to incite a purchase.
In the past if, you signed up for a mailing list and there was no way to unsubscribe, you were pretty much screwed. You could just delete the emails, but they still made it to your inbox for viewing. However, in contrast, it is now far easier to filter mailing list out those unwanted lists. For example, my program gives me this nifty blacklist button next to email addresses - with one click of a button I never see mail from that person again, which by the way is what I used to dispatch those other 18 mailing lists.