^Again: Q is billions of years old. From his perspective, the lifespan of an entire species, let alone a single humanoid, is just a brief moment. To him, the concept of saving their lives barely has meaning, because whether he protects them from an imminent threat or not, their lifespans will still be just momentary diversions for him. If you're having an enjoyable dinner, you may want to make it last and not leave the restaurant sooner than you have to, but you still know it's only for that night and no longer, so it won't be unbearable if something comes up and you have to skip dessert. For Q, having Picard live a few dozen years longer would be nice, but it would be optional, because it wouldn't make any real difference to him in the long run.