My mix produced 2 types of leaves, one very tender, and one a bit firmer. The plants lasted for a very (!!) long time, we were eating them for ages. A good solution for a green manure too! No weeds can survive amongst these sturdy salad leaves!
Please be advised that these salad leaf mixes are best picked as 'baby leaves' similar to the prepacks you see in supermarkets. Grow on a cut and come again basis, getting 3 to 4 cuts then pull out and replace with a fresh sowing.