Formula One, like the Millionaires' Club so often associated with it, is notoriously difficult to get into, while slipping out of it is effortless. The sport's six-decade history is filled with F1 failures; drivers who have made the step up to motorsports' top tier but proved incapable of fulfilling expectations. The result almost always sees team confidence deflate quicker than a punctured Pirelli and a demoralised driver cast aside with little more than a handshake and an all-too-predictable press release. There was once a time when falling out of the sport was synonymous with the conclusion of another Formula One career. Only world champions such as Niki Lauda and Alain Prost were capable of mounting a comeback following an extended absence. In 2010, Michael Schumacher, the seven-time world champion, <a href="http://www.thenational.ae/news/uae-news/schumacher-returns-but-what-drives-a-comeback-effort?pageCount=0">proved once more there is always a race seat available</a> to a proven winner, while the 2008 champion Kimi Raikkonen - courted by Williams in the most recent off-season - has returned to the grid with Lotus for the 2012. This season will feature six world champions and Jenson Button, the 32-year-old McLaren driver who triumphed in 2009, said witnessing the return of drivers like Schumacher and Raikkonen had taught him a valuable lesson. "It tells me not to leave F1 too early," he said. "Two of the six champions have left and come back again. You always think the grass is greener, but you've got to be careful about when you retire. Racing is in our blood and we love doing it." And it is no longer only drivers' title winners who are now capable of returning to the grid. Such is the recurrence of former F1 faces reappearing, the sport appears to be experiencing a new era where sabbaticals are standard practice. Raikkonen's teammate this season will be Romain Grosjean, the Frenchman who replaced Nelson Piquet Jr at Renault midway through the 2009 season, but failed to make the desired impact during his seven grands prix. Last year, he returned as a test driver for Renault and, after winning the GP2 title and taking part in first practice at Abu Dhabi and Brazil, was rewarded with an F1 seat for 2012. Vitaly Petrov made way. The Russian was dropped by Renault (now Lotus) during winter break and, having witnessed first hand how Grosjean had reaped the benefits of remaining part of "the F1 world" said he was desperate to ensure he remained involved in the sport at some level. Petrov signed for Caterham only last month. "I was afraid," he said. "I did not want to miss a year driving, because to come back would be impossible, or at least very, very difficult. For three months, I didn't know if I would be here, or sitting watching TV or back at school or whatever." Like Grosjean, Nico Hulkenburg, having been surprisingly dropped by Williams at the end of 2010, spent last year as a reserve driver with Force India yet returns this year to partner Paul di Resta at the Silverstone-based team. And Pedro de la Rosa, who has spent six of the past nine years as a test driver for McLaren, will be back on the grid as part of Hispania's experienced line-up. Hulkenburg's last grand prix was in Abu Dhabi in 2010, but the 24 year old said he feels no hindrance regarding his lack of action. He went some way to prove such by finishing top of the time sheets during the second pre-season test in Barcelona, but conceded his teammate will have the upper hand early on. "The 14 free practice sessions I drove in during 2011 kept me in the loop pretty well," he said. "But, if there's a deficit, then I will feel it more during qualifying for a race. Paul's used to the procedure of a race weekend and I will have to find my rhythm again first. But this disadvantage will probably be gone after a few races." Schumacher, who has shown glimpses of his old prowess but has yet to be provided a true championship-challenging car by Mercedes GP, told The National that Raikkonen will have a tougher time adapting to the track than the rest of the returnees as technology has developed throughout the Finn's absence. "The main challenge is to get used to the team," Schumacher said of the task that faces Raikkonen. "That was probably the biggest challenge to me, because obviously you need to understand the tyres and the fine-tuning that is slightly different to what we were used to before. It is not difficult to jump in the car and be on the limit in that car, but to tailor make it to your needs … that is what makes the difference, and that is more or less what will be being focused on [by Lotus]." Whether Raikkonen, bored and disillusioned by the end of his last season in F1, has the genuine motivation and determination to try to take a middle-order team back to the front of the grid could have an effect on the future of another Lotus-contracted driver. Robert Kubica, the Polish 27 year old, who has been missing from the sport since a near-fatal rally accident in February 2011, saw his comeback delayed earlier this year after slipping on ice and breaking a leg. Whether he will ever recover sufficiently enough to return to Formula One remains a topic of debate, but recent history provides evidence the pinnacle of motorsports has never before been so welcoming to former drivers. Which is positive news for Sebastian Buemi, Adrian Sutil, Jaime Alguersuari, Vitantonio Liuzzi, Jerome D'Ambrosio, Jarno Trulli and Rubens Barrichello, all of whom have left the grid in the past four months. Only Buemi, a Toro Rosso reserve this year, has remained - as Petrov put it - part of "the F1 world". For the rest, none of whom are former world champions, their sabbaticals may last longer than they hoped. Follow us & Gary Meenaghan