You should make your product as valuable as possible to your users, even if it means reducing the need for your other products, or reducing the time users spend in the product
Of course this maximizes overall adoption and monetizability, but that's not even the most important motivation here. The real reason to do this is trust
The most valuable thing is a good brand, and a good brand is a trust relationship. Your users should trust that what you're doing in their best interests. The long-term cost of playing tricks is immense
For instance, if you decide to send a notification email, it should provide useful information and it should be worth your user's time. It should not be a trick to get them to log back in to inflate MAUs
