It is my understanding (possibly mistaken?), that after a major upgrade iOS reindexes spotlight metadata. This is done in the background, but drains battery and

It is my understanding (possibly mistaken?), that after a major upgrade iOS reindexes spotlight metadata. This is done in the background, but drains battery and kind of makes the device perform a bit more slowly. Same day right after an upgrade, my phone tends to be a bit pokey and the battery drains pretty quickly. Next day after an upgrade, my phone usually "feels" fine again and battery life is back to normal.