Initial Index GridView Filter

Could someone help steer me in the right direction for the following.

I have an index view with a paginated Gridview. It all works beautifully. This main view dataprovider is quite intense pulling from numerous tables … because of the number of daily entries, we’ve been noticing a slowdown in load over time. What I’d like to do, if possible, when the view is loaded only see the last 3 months of data (StartDt field), and if the user applies a filter then pull from the entire database.

Is something like that feasible? How would one approach this?