Growing Spinach
Spinach likes cook conditions; too hot for too long and it will bolt. But even in the best conditions, it won’t produce leaves endlessly. The harvest season, and the best conditions, also depend on the variety. Ballpark estimate of harvest season in ideal conditions: six to eight weeks. You might find more help below—there is lots of information there, including, maybe, the variety you are growing.
Kale starts best in cooler conditions, and it might appear to slow down in heat. Here, too, the harvest season, and the best conditions, also depend on the variety. You might find more help here; be sure to read the questions and answers at the bottom of the page, too—there is lots of information there, including, maybe, the variety you are growing: http://www.almanac.com/plant/kale