If you have the Heat Rises buff active and consume a grenade the timer is always reset to 15 seconds. Eg: Heat Rises: 0:25 immediately lowers to 0:15 Also (and I'm not sure if/how this is a bug) Touch of Flame states it's own base cooldown as 2:01 but Firebolt grenades still recharge as default (1:04 at Tier 3) with both equipped.