Apparently they've been together since Zeus married them upon Herc's apostesy.  They've never officially split-up, they've just been separated.   
 
Herc, it's widely known of course, has spent most of their marriage philandering (that's a fancy way of saying cheating on his wife).  Herc's behavior is obviously less than ideal for a hero, but during the "Assault on New Olympus story-arc he and Hebe seemingly reconciled so we'll see if that is even remembered let alone used in Herc's future story-lines.   
 
Personally, I like the idea of Herc pairing with many of Marvel's super-heroines (and some villainesses, too).  Though this flys in the face of the heroic ideal, it fits well with Herc's rakish charm and flawed persona. 

"@PowerHerc: I kind of like the idea of Herc beening with differnet wemon to like She-Hulk, Ms Marvel and others but I fill bad for Hebe to. "

Whether Herc ends up staying with Hebe or not, I doubt he'll ever find a woman who'll worship him like this again.