Narakasura, the son of Lord Varaha and Bhudevi, is quite famous. It is because of him that Lord Krsna was able to get the name Murari, Narakari, as well as whole festival dedicated to him (Deepavali). Oh, also Krsna was able to marry 16100 princesses.
Narakasura's story is described in the 59th Chapter of the Dasama Skandha of Srimad Bhagavatam (as well as many other scriptures, but we will restrict ourselves to Bhagavatam in this question). Since he is the son of Bhudevi and Varaha, it can be logical to assume that he could have been born anytime from the beginning of our Kalpa to the beginning of the Vaivasvata Manvantara.
That he is very old is vouched for by Sugriva in the Ramayana, where in the Kishkindha Kanda, Sarga 42 he directs the monkeys to search for Sitadevi, but cautions them against going to Narakasura's kingdom (Sloka 31).
Also in the Mahabharata, Udyoga Parva, Chapter 130, Vidura tells everyone how Krsna slew Narakasura, who was Aneka Yuga Varshayuh, 'Of Many Yugas in Age' (Verse 44).
But taking all this into consideration, it is surprising that Narakasura would remain dormant for so long and attack Svargaloka only when Krsnavatara happens. At least, that is what is presumed from the 59th Chapter of Dasama Skandha, where it is said that having lost all his riches, as well as Varuna's umbrella and Mother Aditi's earrings to Narakasura, indra rushed to Krsna for help.
So, did Narakasura really wait that long to attack Svarga? Or did Indra just wait for the right time and right person to lodge his complaint? If the latter is the case, when exactly did Narakasura conquer Svarga?