I'm one of the founders of OneSignal. Here's some of what we've seen our clients do for each of these: a) Push notification fatigue You should treat notificat

I'm one of the founders of OneSignal. Here's some of what we've seen our clients do for each of these: a) Push notification fatigue You should treat notifications as you do any other major product feature. This means seeking to experience the feature yourself as a user would, doing user research & interviews, and instrumenting analytics around this. In general, you should make sure that notifications are very useful to your recipient as often as possible. For notifications that make a vibration/sound, aim for 50%+ of notifications to be very useful. For notifications that do not play a vibration or sound, 20% is a reasonable target. b) Lifecycle of push notification Tools like OneSignal help with this. We recommend setting up a well-thought-out series of automated messages, or scheduled messages, based on user interactions. c) Push notification open rates OneSignal and other tools provide this data. Keep in mind that open rates are just part of the picture -- users often open the app directly after receiving a notification. In OneSignal this is tracked as an "Influenced Open". Furthermore, make sure you're tracking CTR against notifications actually received by the device, not just notifications you send (Some notifications may have been "sent" to devices that are no longer active and won't receive it). Whether you use OneSignal or build notification support yourself, this is an important metric to instrument correctly and keep an eye on.