I second that. There's almost never a reason to ever firebomb, ever. Ever. Eeeeveeeeeer.

If farming for idols: Reset shortly after you stop instakilling. If you have bonus idols unlocked, you might get to the 5th area of a section with relative ease even if you stop instakilling during the 3rd area, but after beating the boss, don't go for another set of 5 areas

If completing objectives: If you can't do an objective easily, then don't do it. Firebombing is a last resort after tanking, and if you've begun tanking to try to push to the end of an objective, you, are, not, strong, enough. It isn't worth the effort. Just farm more idols/gear/talents.

Like Teschio said, the only real exception is if you're really close to area 1500 and want to push to unlock those talents, and even THAT is a one-time thing. If you ever use firebombing, regardless of how frequently, you're only hurting yourself with massive amounts of wasted time.

Jasmin, glad to have been able to help. Since you've hit area 1500 and unlocked those talents, let me tell you nice and early that "Every Little Bit Helps" is incredibly overpowered. So here are some tier-5 talent tips...

-"Bonus Training" works by adding 25 levels to the level cap for crusaders based on how far right they are on the bench. Ergo, level 1 adds 25 levels to crusader slots 1-27, then level 2 adds 25 more to slots 1-26, etc. Since I use Chiyome as a main DPSer, I only have the talent at level 3, since anything past that would stop benefiting her. Use your idols on this talent first. It's a cheap way to buff your level cap.

-"10K Training" should be your next target, but be reasonable with how much you dump into this. This talent takes priority over the ones I'll mention after this, but still try to not focus TOO much on it because...

-Again, "Every Little Bit Helps" is incredibly powerful. 25 more levels to the level cap effectively gives you 300% more DPS (at the end of a run), which takes ELBH 29 levels to match (for the entire run). ELBH is extremely cheap. You should be able to easily level it up to almost 100 with relative ease; at LEAST level 50, if you currently have 18M idols. The cost per level barely goes up each time, so it's easy to estimate how much 29 levels might cost. I personally use the formula (current cost * 29 * 2) to roughly estimate the additional cost per level by the end of 29 levels. If it comes out to LESS than the cost of a single "10K Training" level, then I focus on ELBH for a while until I begin feeling like ELBH has started to become less easy to level up. Then I revisit the formula just to check.

-"Idol Champions" can be a godsend if you DON'T have bonus idols unlocked on every chapter. If you've already got all bonus idols unlocked, then putting some levels into this talent can still be helpful, but don't go broke on it. Give it some honest attention, but don't obsess over it too much. Focus more on talents to buff your DPS so that you can push deeper into areas for more bonus idols instead.

-"Cheer Squad" and "Valuable Experience" are additive, which immediately makes them kind of crap compared to ELBH. Buy a few levels while they are nice and cheap, but really, you shouldn't be giving them much attention by the time they reach 10, if not well before that point. I have ELBH at level 166, which gives me a 329K% buff and still only costing 926K idols, compared to Cheer Squad at level 15 giving 15% per (about a 255% buff) and costing 1.64M idols, and "Valuable Experience" at level 13, effectively buffing my damage by 260%, now costing 2.5M. So exclusively level up ELBH until it begins costing a bit too much for you, then start sprinkling in the lower levels of CS and VE.