Every good reality show relies on two main elements: sexual tension and a crescendo of events leading to a surprising conclusion.
   Fox's new show will clearly have the sex, but not the crescendo with a program that will go on and on and on without any foreseeable conclusion. 
   Neither Fox nor no one else, for that matter, knows what the end of "Forever Eden" will be. What Fox does know is it has to do something to patch a schedule with holes on Monday, Thursday and Friday, and a potentially neverending supply of "Eden" episodes could help.
   Fox has ordered 25 hour-long episodes of the series, from the producers of last summer’s reality dating show “Paradise Hotel.” Much like “Paradise,” the new show will feature single men and women who live in isolation in a luxury resort. 
   But unlike any reality show before, “Eden” will have no predetermined conclusion. Instead, contestants will be urged to continue living in the resort -- and on the show -- indefinitely.
   Just how that will appeal to viewers, who have no big conclusion such as choosing a mate or winning a contest to look forward to, is also unclear.
   Similar to “Paradise,” the cast will remain fluid, with some people leaving and new people joining the group, but the main constant will be their lack of contact with friends and family. Producers are still working out details but say contestants may be able to earn rewards like a 10-minute phone call home.
   True to the spirit of a reality show, the singles will earn money during their stay. If they leave the show on their own, they forfeit the money, but if they are chosen to leave by their housemates, they can retain half of their earnings. 
   For additional drama, the show is also expected to include surprise guests who visit the resort, like former cast members or people from the contestants’ personal lives.
   Fox executives don’t expect the show to draw huge ratings initially, especially given the duration of the program compared to previous short-run reality shows like its own “Joe Millionaire” or NBC’s “For Love or Money.” Instead, the network hopes to create a constant, reliable show that lasts months or possibly years. 
   While Fox has not announced a start date for the show, “Eden” is expected to premiere in the next few months. 
   The show could fill any number of rough patches in the network’s schedule after three early cancellations. The axing of “Wanda at Large” and “Luis” on Friday has weakened the night for an already struggling and rescheduled “Boston Public.” 
   And “American Juniors” was expected to keep audiences excited for January’s new season of “American Idol,” but weak ratings over the summer put the show off the schedule for the fall.
   But Fox will probably schedule “Eden” for Mondays at 9 p.m., an hour left open since the early cancellation of new drama “Skin” and the former home of “Paradise Hotel.” 
   The show could also fit in the specials-laden 9 p.m. hour on Thursday, but it’s a poor complement to “Tru Calling” at 8 p.m. and the competitive Thursday night line-up on other networks is likely to stifle a late-season debut.
   But if “Eden” is able to draw decent ratings, Fox is likely to use it for multiple episodes in a week to fill holes in the schedule. The network has already done that with current hit “The Simple Life.” The benefit for “Eden” is that its ongoing storyline and taping means it will never run a repeat, but its hour-long format makes it more difficult to schedule for Fox, which has only two primetime hours a night.
   While “Eden” bears some resemblance to “Paradise Hotel,” Fox isn’t ruling out the return of the latter next summer. That series, as well as lead-in “Anything For Love,” was often bested by NBC’s competitive reality line-up of “Fear Factor” and “For Love or Money” over the summer, so its return may be scheduled on a different night.