As I mentioned, I love my oven-safe alarm thermometer because you don't have to worry about timing, it will let you know when the desired temperature has been reached. However, if you don't have one of these no worries! Just check the thighs at the 30 minute mark with a regular meat thermometer. If your chicken thighs are small, you may want to check a bit sooner. If needed, you can always put the chicken back in the oven for a few more minutes. By the way, even if you happen to overshoot the final temperature, you should still end up with juicy chicken. The dark meat is already more juicy than white meat, and the skin also help to retain moisture. So don't sweat it too much. Just remember, 165 degrees and above is the safe temperature to consume chicken. Plus, I like to cook dark meat to 170 or even 175 degrees to help dissolve the connective tissue, as recommended in this article by ThermoWorks.