Custom Dimension - When To Send User Scope Custom Dimensions

I am currently trying to add a user scope customs dimensions to our mobile app(both Android & iOS).

I want to send the Login status, Age, Review Count data of our app member so that I can set them up individually as segments.

But I'm not sure when to sent the info. I originally thought to send each custom dimension at 'screenview' but can I send more than 1 custom dimention for every screenview?

Our iOS developer suggested to only send them when the app comes back from to the foreground, but would it work the same as sending them at 'screenview'?

Thanks

You can send across as many custom dimensions and metrics in one hit as you like, up to GA's 200 limit and assuming you don't exceed the 8192 byte limit.

If you send the data more than once, it will just replace the existing truth for that user, given that you are working with User level dimensions.