On default settings in Arcade mode, with the two 1-ups, you're working with five lives. So what would a good run for me be right now?

Stages 1 and 2 should be beaten with no deaths.

Stage 3 I might die once, due to gettting sandwiched or using my mosquito too long.

Stage 4, even with a risky, high point playing style, should be doable with no deaths. The boss is another story. 95% of the time I lose two lives there.

So that puts me at stage 5 with two lives left. I'm good enough at the stage now that I don't die more than I lose a life. But the final forms of the boss almost always gets me once.

Thus, on a good run, I'm at stage 6 with one life. Only problem is I rarely have good runs. The first time I made it to stage 6, I had 3 lives left, which lasted until the final boss.