What? What do you mean by exploited?
I usually only had about the same amount of life (usually less, so I had to find health just to enter hypermode).
Normally the Phazon meter will deplete when you fire Phazon shots. Later in the story, the "emergency shutoff" stops working, so after 20 or so seconds of the mode being active, the meter will gradually regenerate/overload, therefore you have to fire shots to keep the meter from filling up and killing yourself. Basically, you have extended invulnerability time and ammo because the game is gradually providing free refills. Wait for a refill, fire a shot, repeat, and the mode eventually shuts itself off safely. Bosses are killed in like... no time?
Ever since the game explained in the beginning that the mode was supposed to shutoff automatically, I LEFT IT AT THAT. I didn't see a point in keeping it active a long time since it wasted quickly, so I either fired all my shots while a boss was vulnerable or I jumped in/out of the mode to "conserve health."
So the hardships I cherished turned out to be just a dream.