KCamaro

I'm looking to purchase my second LS1 car. My plans are to make this a cam/n2o car. Is there any specific point in mileage that I should try to avoid? e.g. one point in time a car is too over the hill to mod enternally or add a power adder. any help is appreciated. I know that there isnt a specific mile every car would be unsafe to mod heavily but a ball park to start avoiding would be appreciated. Thanks in advance