There are 5k, 10k, 25k and 75k glowpowder quests in nether. One tree gives about 100-125 of glowpowder and takes (as for me, idk if im just slow) ~2 minutes to chop. So if we calculate, we get 100, 200, 500 and 1500 minutes of pure destroying of glowstone blocks, so it takes 38 HOURS of active...