Why not mean both?
I mean, when you fall in love with someone and are on your first date(say), do you ever look at your watch? And how many times do you , when you are in a lecture hall? The difference is, in a lecture, no matter how much interesting it is, when it crosses say an hour and a half, (even if everything you are learning is new and beautiful) you stretch yourself slightly from the current posture , and have a look at the watch. So posture may be the thing a part of your mind is getting "bored with"(metaphorically), even if the rest of the entire brain is consumed in the lecture.
In love, the lover want's to mean(scientifically) that not a single part of her body is getting bored, i.e. every moment is refreshing and rejuvenating for her.
Every single second feels new. You do not remember a single event of your previous life,do you?(except in case you are extra special!) Every lifetime is independent(mathematically ;-) ).
Lifetime in a minute is also used as a metaphor to indicate her extreme happiness: she means the entire joys and happiness one experiences in a lifetime, combined together are equivalent to what she is experiencing every moment.