is there any real danger in having a 2 and a half - 3 hour session?
At a certain point your body goes into a katabolic state where it eats its own muscle. That is why people limit lifting to that time frame. If you lift longer you will need to have a protein and carb source halfway though at minimum. But training longer isn't harder. Split those sessions into two or shorten them to get results or you will over train.

leider hab ichs grad nur auf englisch gefundn, aber ich denke das erklärts genauer