It depends on whether you have a balance with walking meditation. Sometimes with walking meditation you get the balance with letting go of thoughts. We don't want to just be making thought without developing the capacity to let go of thought and note the hindrances objectively, because this is quite important in our practice. If you can incorporate five minutes or so of walking meditation before you do your 20 minutes, it could be very helpful. Or perhaps five or so at the end of your reflections, at the end of the 20 minutes could be helpful, so we don't lose that capacity to let go of thought and just note the hindrances.
But we don't want to make it too difficult either. Because if you really do like your the Compassion/Lovingkindness practice, we don't want to replace it with a practice that is too hard and we don't want to let go of reflection, thinking that we have to watch the breathing all the time. So having a balance on that would be very helpful. And it may be helpful throughout the day when there is a bit of a lull between activities to just focus on the breath a little while, and just watch a few breaths, so we get an inner chance to watch it in our day and let go of thought.