Do you display different offers to users who have already subscribed to your email list?
If we don’t keep pushing the same offer face to face, why do it online? Why keep presenting the same content to our users, same things they already signed up for, same redundant offer?
Better to differentiate the kind of content people see, the content new users see compared to the one shown to existing subscribers. Show alternate content to your users, for example show opt-in forms for ordinary visitors and upsell offers to your subscribers.
Take your lead generation setup to a new level, considering the post-subscriber state for, for example, presenting special offers. Show different content for different users: forms, offers, opt-in options etc can be different if you don’t want to annoy your subscriber visitor with 1st time subscribe popup windows, email subscription forms etc.
I encourage you to take a big step forward your visitor differentiation, targeting and engagement.