Place 3 racks equal distance apart in your oven and preheat to 225° F.
Pour half the contents of each snack bag/box into an oversize bowl. Mix gently with a large spoon or clean hands. Add half of what remains in each box and mix well. Repeat. (This just makes it easier to mix thoroughly little by little.)
In a small saucepan, warm oil and ranch seasoning sachet over low heat. Whisk until mixed well and gently warmed, 2-3 minutes.
Pour 1/3 of the mixture over the snacks and mix gently, turning the bowl a quarter turn as you stir. Give the butter mixture a quick whisk again and pour half of what remains over snacks. Repeat. (Again, this just makes it easier to coat gently and thoroughly).
Spread evenly between 3 cookie sheets.
Place in the oven and cook on 225° F for 90 minutes, rotating the sheet pans from high to low and gently tossing every 30 minutes. (Tossing is optional)
If bagging, cool fully 20-30 minutes.
Bag up and enjoy!