Okay, so I finished mission 40 on SRTOG2, on my third try. First time out, I did not realize this particular mission would feature not one, not two, not three, but FOUR bosses, one right after the other. The thing about bosses in SRTOG2 is that they regenerate HP each turn, so you have to do your best to finish them off in one or two turns or you'll have lost all your progress. The other thing is that they are usually either extremely hard to hit, or they counterattack for so much damage they'll instantly kill your unit. Which means that you have to use up SP to activate abilities to raise your hit rate and your dodge rate...and your SP is limited.
The first time around, I finished up the first boss by maxing out all my characters' hit rates and dodge rates...finished him off in one turn, and then TWO bosses popped up. I was barely able to finish those two off, when the fourth one appeared...at this point, I was out of SP, so there was basically no way to beat him.
Second time around, I equipped most of my units with SP drinks so they could gain back SP once they reached the fourth boss. So I got to the fourth boss and his HP would...NOT...go down! I kept hitting him for massive amounts of damage, but nothing...I finally got him down to 99,999 HP and I was out of SP and SP drinks. Failure.

Third time's the charm, though...this time, I knew what was coming and planned accordingly and whupped his ass just two turns after he showed up. This is the first time this has happened to me in the game...I've been able to finish each battle so far on the first try, albeit with judicious planning each time.
Anyway, I started mission 41 now, and I think that one is probably the next to last one, since I've basically finished off all the enemy characters that have appeared in the game except for two (who I imagine are the last bosses - but who knows, there are so many rival factions in this game...).
After I finish STROG2, if I get the option to start a new game plus, I think I'll start it over since I apparently missed out on two secret units, and the game has alternate paths I haven't explored yet. But if I have to start over from scratch again (like in STROG1), I'll move on to another game.
EDIT: BTW, this game is a lot better than OG1. Where OG1 had a mediocre story (lol, story in an RPG) but great battle system, OG2 improves the battle system and while the story is still typically overplotted and ridiculous, it is at least extremely entertaining and full of soap opera-ish twists and turns that keep you interested in the cut scenes between the action.