I would not disagree with anything Yogani says because of his immense wisdom and kindness. But if I feel the need to meditate more than 1/2 hour twice a day and feel no bad side effects, would that be okay? Like the Zennies do.
The difference with the Zennies is that they don't use a mantra (I think), they count breaths, so maybe they can do more of it. I used to meditate like that for an hour and didn't have any problems.
However, using a mantra could be different for you: for me using the mantra for 20 mins is just right. Otherwise I get a right stonking headache.
I understand you want to do more and make progress. I would suggest adding more practices than doing same practices for longer time.
Go through the main AYP lessons and add the next practice after what you are doing. Self-Pace and if you do well then add the next practice. Like that.
I tried doing extra meditation sessions in a day but in few days I can feel the overload. Still on some saturdays I add an extra session after my morning's session.
Something powerful like Yoni Mudra Kumbhaka might keep your bhakti at bay. And it would be better than increasing meditation time; just thinking about it is bringing on a headache.