During the first trip, I doubt there was much sex for Berto as though he tried to act older, he was only 14, maybe verging on 15 (Only Rahne was younger than he was on the team), and as noted, most comments about Berto were "Cute, but he really IS a child", so I can't see him having that much appeal to immortal partners on Asgard (even if a Midgard lad could survive the experience when the average Asgardian measures their strength level in tons!)

As for the second trip, sometime in the interim between Doug's death and Cable coming on board, the team spent several issues in Asgard, which ended with Dani staying behind in Asgard as a Valkyrie rather than returning to Earth (Which is why she never worked with Cable on the NM team)