(CNN) -- Emma Loggins' boyfriend was out of town, and she knew what she had to do.
It would take some time -- and certainly some commitment -- but she was determined. After all, just about everybody she knew did it. Her boyfriend would have done it with her if he were around.
So she sat down, got comfortable -- and in a furious spree, she watched four seasons of the television show "Lost" in three weeks.
"You have to, with a show like 'Lost,' " said Loggins, who runs the site Fanbolt.com. "I wouldn't have wanted to watch it season to season because it would have been agonizing for me. It was wonderful to be able to watch episodes back to back and not wait in between."
Loggins is just one of countless viewers who has engaged in such marathon viewing sessions.
Whether to get ready for a new season or to just be able to join the water-cooler conversation, people are spending hours watching back-to-back episodes. Whole weekends can fall by the wayside as fans dig into past episodes of shows. Once it starts, some say it almost becomes an obsession.
The DVD set of season five of "Lost" is among the top 20 best selling DVDs on Amazon.com and has been in the top 100 for more than 200 days. Other big sellers include past seasons of "True Blood," "Dexter" and "Bones."
Mary McNamara, television critic for the Los Angeles Times, said many of today's television shows have such complex story lines that viewers often feel the need to rewind.
"There's just so much that happens in a given season and then people forget, so they want to reacquaint themselves with the narrative," she said. "Also, I wouldn't be surprised if a lot of the shows that people do this with are shows that are sort of like alternative universe shows where you have to get into the mind set of the show.
" 'Lost' is the ultimate example of that, because you can't really try to make sense of 'Lost' -- because there is no sense to be made of 'Lost' -- so you just have to surrender to the wide ocean of the writers' imagination," she added. "To do that, it's easier to just submerse yourself."
David Bushman, a curator of television at the Paley Center for Media in New York, said the availability of series on DVD and at sites like Hulu.com enable viewers to be able to engage with a show on a different level.
He cites HBO's "The Wire" as an example of why many people say that well-done episodic television is now the new version of the serialized novel. (HBO is owned by Time Warner, which is also the parent company of CNN.)
"The show was so brilliantly done that there was stuff that happened in episode one that may not pay off until episode 13," Bushman said. "In a lot of ways if it took you 13 weeks to get to episode 13 you might not even remember episode one, so if you watched it straight through you got the payoff better."
Critic McNamara said TV fandom, in general, has evolved to a level where only small groups used to boldly go.
"Now you have, like, these TV savants, people who just keep track of the minutiae of some of these shows that previously you only saw with Trekkies," she said.
Erik Wilkinson, one of the bloggers for the TV fan site Give Me My Remote.com, said a marathon helped him become a fan of the critically acclaimed show "Friday Night Lights" when he was laid up in bed for a few days.
Today's viewers are juggling so many obligations that fitting in shows when they are actually airing can be a challenge, he said.
"Nowadays the toughest part about being a really loyal TV viewer is packing in as many hours as you can," Wilkinson said. "Through social networks like Facebook and Twitter you hear a lot of chatter about shows that you may not have thought about watching otherwise."
Jon Lachonis of TV OverMind.com said viewers can become obsessed with finding out what happens next.
"With a show like 'Lost' that has a sense of mystery, going back to review might reveal a new understanding or you can catch a little hint or discovery," Lachonis said. "But a lot of times I think it's just sheer obsession."
Not even television critics are immune. McNamara said she and her husband watched the first and second seasons of "Damages" and enjoyed some preview episodes she received as part of her job as a critic.
"At the end of the last one he said, 'Where's the next one,' " she said, laughing. "I said 'We don't have the next.' He said 'What? We have to wait until next week?' I said 'Yes, it's called television.' "