I'm using 10 sec exposure on hero4 silver Usually with no interval The battery runs off after about 2.5 hours
If I'll increase the interval time, will it give me longer shooting time?
In my testing, NO. I used a 60-second interval (see video) and the battery lasted 136 minutes, and I have repeated this test a few times. Your best bet is to do what I did and buy the battery charger, which will charge a battery before the other one runs out. Then, during your interval at some point, change the battery and re-start the time-lapse. You can do that indefinitely.