Adjusted cooking time for an already-baked pie shell I have a pumpkin pie recipe that calls for an unbaked pie shell. During the cooking step, it cooks first at 425&deg;F for 15 minutes, and then at 350&deg;F for 30-40 minutes (until toothpick can be inserted cleanly). My understanding is that the first bit of cooking, at 425&deg;F is to finish off the (frozen) crust, and then the 350&deg;F is to cook the filling through.

At the moment, I have no unbaked pie shells, but I do have some graham cracker crust pie shells that I would like to substitute in their place. I figure that since the shells are 'ready to eat' already, they don't need the initial 425&deg;F cooking step. Since the pumpkin still needs to cook and set, I would need to somehow extend the 350&deg;F step accordingly to account for the cooking done in this initial stage, if I omit the 425&deg;F step.

My basic plan is to fill the crusts and then bake at 350&deg;F for about 50 minutes. Then continue baking until it passes the toothpick test (checking every 5 minutes or so.)

Is this a reasonable plan, or should I instead retain the 425&deg;F initial baking phase even though the crust itself doesn't require any cooking? Or are the graham cracker crust shells entirely unsuitable for this project for some reason I'm overlooking?

(I'm following the basic Libby's "new fashioned pumpkin pie" recipe, which I've used previously many times with frozen pie shells.)
Most pie recipes that begin with a high-temperature setting and then lower it are to bake the crust.  It isn't necessarily for frozen crusts only, but also for fresh-baked crusts that often need high heat to set and create the "flaky" pastry texture that many people desire.  (Also, unbaked crusts can absorb too much liquid on the bottom before they set without this high temperature step.)

If you're using a pre-baked pie shell, you're correct that this high-temperature step likely isn't necessary.  In fact, it's probably better not to use a high-temperature step on a pre-baked shell unless a recipe calls for it, as excessive crust browning is a problem with many pies that bake a long time to begin with.  (Which is why people often use foil or pie covers toward the end of baking.)

Anyhow, your plan sounds reasonable -- bake for a bit longer than the original total recipe time to account for the decreased temperature, and then begin checking periodically for doneness.  (And as there are a number of pumpkin pie recipes that use graham cracker crusts, I assume they should be fine for most recipes.)