Yes, that is normal in healthy relationships. You should gain emotional energy and emotional stability from them. My girlfriend and I are both introverts, but we can spend hours together with no problem, while if we spend the same amount of time with other people we are very drained. We still do need alone time, but it's not the same as spending the time with other people, even close friends.

Right - and you should avoid relationships where both people aren't on net gaining energy and time.

Extrovert/introvert "recharching" works because extroverts/introverts by definition like social activities/solitude. The general principle here is that people are recharged by spending time in a manner which they find simultaneously comfortable and engaging ("flow"?). An intellectual is recharged by thinking, an artist is recharged by creating, a romantic by romance, etc.

Beyond the obvious foundation of mutual love and affection, a good relationship is somehow creating or enhancing these dimension of life that you are energized by. On top of that it should ideally actually seem to free up time, as cooperating with a partner to tackle things generally cuts down work load, but even if it doesn't, if you've got the mutual love and mutual energizing in place I'd count it as a win.

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