I use location a lot in my app, and I've found that if the user moves far away (i.e. on vacation to a different country), the app shows a permission popup asking the user if they really want to keep location permission as always soon after. I've also found that providing some message from the app (i.e. in notifications) helps a lot more than what I can put on the permission popup to remind the user what this permission is used for, and helps my users make more informed decisions when they are asked about the location permission. Is there any best practices or heuristics I can use to decide when to show this notification? I just have some pretty simple logic in my app today, but would love to be able to provide a better experience.
There is no way to predict when the usage reminder prompt will show. However, it is reactive to changes in location usage (that is, receiving location updates, significant location changes, condition/region events, etc).
Your app likely gets more such updates/events when the user is traveling, so that will tend to accelerate presentation of the usage reminder prompt.
If you find that presenting a notification to explain why your app uses location is helpful in guiding users to make more informed decisions, then that is a reasonable thing to do!
