The pair started actual embrace at around 3pm, ending at around 6pm. This time the mating took around 3 hours.
It wasn't all fun and games, at one point the male nip the female so hard she hid under the driftwood and "leak" eggs. I estimated around 30 eggs was wasted during that time.
I am not too optimistic regarding the current mating session. The male did not wrap over the female from the top. Instead he did a novelty act, warping her from the side and the female eject her eggs rather prematurely after the warp. This was exactly what happened last mating session.
The female is taken from the breeding tank for recuperation in a 1 gallon tank. Fins are pretty badly damage. Looks like she needs a very long break to recover. If this mating session is another failure, a retry should come in 4 weeks time or until her fins have heal up. I do not want to risk losing my only butterfly female.