Hi Marlorena, assuming this is still of interest to you, I got a top-grafted weeping standard plant of New Dawn from Beales in 2014. I garden in containers on a patio and quickly realised it was not suitable (in fact, it was a hazard!) in that space. So after it bloomed I planted it in the ground, on an island that belongs to the river-side building where I live. The soil is poor, hard and gravelly; I never fed it and it was really planted too close to an ash tree. The stake also did not hold, so it spent much of its life on the island leaning on one side. I hardly ever watered it, pruned it, or dead-headed it. Mostly I forgot about it, being half hidden by the ash. In those conditions it never has spectacular blooming in spring/early summer, but it's always had some flowers in the autumn. Nothing to write home about, but still. My conclusion is either that top grafted specimens of New Dawn rebloom more readily, or that poor soil restrains green, vigorous growth, and encourages rebloom. I have just potted this up again and am training it over the arbour of a bench, as the flooding this winter washed the soil away and left it with almost entirely exposed roots and lying completely flat. We'll see what rebloom I'll get in the conditions (being positioned close to a north-facing wall, probably not much).
PS: I have just checked some past HMF comments on this rose and I gather that not deadheading might have helped with the second flush; this is because in wichurana roses 'new buds grow very closely behind the spent flowers', so one should be 'Careful not to prune off the not yet fully developed buds immediately behind the just bloomed flowers' when deadheading. This was advice from the now passed away owner of Azalea House Flowering Shrub Farm (NY).