That's a good question!
To help address this issue we have provided the following features and options which will be available during the RC.
1. Interface availability will roll up status polls and store a row into the _Details table at a rate of at most as frequent as your statistics collection. (So by this it will store data every 5 polls given the default poll values - so a _Details record that had 4 up and 1 down poll would store a 0.8 value as a weighted calculated value) Therefore, by default, the InterfaceAvailability_* tables will be at most as large as your InterfaceTraffic_* and InterfaceErrors_* tables from a row count perspective.
2. Interface Availability historical storage to the database can be turned off on the entire system (to be have like pre 10.2 versions) or turned off on an interface by interface basis.
3. The InterfaceAvailability_* tables will have their own summarization schedule so that you can keep data for less (or more) time than your other tables.
Please give us any feedback about these items that you would like to.