Sounds like an useful service. Though, I'm not sure whether email bombarding is a good idea. You used the example of AppSumo but I unsubscribed after 3 emails sent too close together. Most people don't unsubscribe but rather just ignore the email. I don't need an email every time a small feature is released, or pushing me to come back... there's a reason I don't revisit, and it's not because I forgot. What I like are…
It definitely sounds like a lot of emails in my article. But let's say you never engage with the service. You might receive 2 in 2 months and then never hear again. Smart, not abusive. While I mentioned reminders often as it's easiest to describe, "Teach me something new." is exactly right. Engaging mailers should offer help, tips and such.
That's precisely what I did with my Gmail account when it became near-unusable after I used for several signups for startup services which I eventually was not interested in - just signed up to try out. Someone send me an email that does not pay me back with something useful for the minute of the attention I spend reading it - I create a filter to send it to 'adware' folder, which rarely, if ever, gets read.
This is of course my personal behavior, which may or may not be more typical.