5 minutes and 10 seconds for ON-TIME
0 minutes and 02 seconds for OFF-TIME
The 555 doesn't show any trouble with the duty cycle, this circuit works just fine. I tested for several hours, I recorded the length between the ON and OFF cycle. I also recorded the cycle length after pressing the switch (which resets the countdown). I spent hours doing just that, and I didn't have any issued at all. Sometimes the ON-TIME will be 5 seconds more or less, but it's just around 5 minutes and 10 seconds, which is perfect.