Perform stream calculations in app "brain" - An alternative to Stream Builder - firebase

Question

I am listening to a number of streams with RxDart. I then use a StreamBuilder to process the data as it comes in and update String and int variables that I then display in my app. Streams and variables are displayed below.
Stream<QuerySnapshot> janFlightsStream(BuildContext context) async* {
final uid = await Provider.of(context).auth.getCurrentUID();
yield* Firestore.instance
.collection("UserAirTravelInputs")
.document(uid)
.collection(formatDate(DateTime.now(), [yyyy, '', '']))
.where("entryMonth", isEqualTo: "Jan")
.snapshots();
}
Stream<QuerySnapshot> febFlightsStream(BuildContext context) async* {
final uid = await Provider.of(context).auth.getCurrentUID();
yield* Firestore.instance
.collection("UserAirTravelInputs")
.document(uid)
.collection(formatDate(DateTime.now(), [yyyy, '', '']))
.where("entryMonth", isEqualTo: "Feb")
.snapshots();
}
double janFlightsKm;
int janNumberOfEntries;
StreamBuilder returns a widget which is fine here. But I do this on each screen in my app which is extremely inefficent. I want to extract this logic (of listening to firebase stream data and making calculations based on that data) from each screen to something like a provider or app "brain" which handles this data, so that I only need tp access the output of these calculations when needed in the different app routes.
StreamBuilder<List>(
stream: CombineLatestStream.list([
janFlightsStream(context),
febFlightsStream(context),
]),
builder: (context, snapshot) {
if (!snapshot.hasData) {
return Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
SpinKitDoubleBounce(
color: kDarkBlue,
size: 100,
),
Text("Loading data..."),
],
),
);
}
if (snapshot.data[0].documents.length != 0) {
final janFlights = snapshot.data[0].documents;
double janTotalGCO2e = 0;
janNumberOfEntries = snapshot.data[0].documents.length;
for (var flight in janFlights) {
double janKm = flight.data["flightKm"];
janTotalGCO2e += janKm;
}
janFlightsKm =
double.parse((janTotalGCO2e / 1000).toStringAsFixed(2));
} else {
janFlightsKm = 0;
janNumberOfEntries = 0;
}
if (snapshot.data[1].documents.length != 0) {
//Do something
} // Do something else
return Scaffold(
backgroundColor: Colors.white,
appBar: AppBar(),
body: Container(
child: Column(
children: [
Text(janNumberOfEntries.toString()),
Text(janFlightsKm.toString()),
],
),
),
);
}),
Is there a way to do this without using this repeated StreamBuilder? I have looked in to StreamProvider but appears that only gives the stream of data, and I would then have to process the data again each time I tap in to the StreamProvider which does not solve the problem.
Simply it is 1. list of streams. 2. process data coming from streams (as code above), 3. store that data, and 4. make it available throughout the app.
Any help would be greatly appreciated!