Every club, and every manager's job, has its own shelf life but none of those who decide on the big three jobs in Scotland – the national team, Celtic and Rangers – would have shown the tolerance and understanding displayed by Arsenal. Wenger will enter a ninth year since bringing a trophy to north London. In Scotland, the shelf life for an underachiever is three years, at most.
The average longevity of a coach under Roman Abramovich at Chelsea is eight months, which amounts to a grotesque addition to the guillotine. The turnover of managers at Stamford Bridge has made the club look absurd. Yet, slowly but surely, season after season, Arsenal's alternate approach has attracted growing ridicule, too. Tame, undemanding, mediocre Arsenal: content to put up with decline from a manager who has lost his touch as they slide towards irrelevance. As far as Manchester United, Manchester City and Chelsea are concerned Arsenal can keep Wenger for as long as they like; the club is no longer a challenger under him.
In some ways, the maturity and respect shown by Arsenal towards Wenger typifies a club which epitomises old-school class and dignity. Arsenal are too sensible to make decisions based on short-termism or impulsiveness. But there comes a point when an admirable ethos begins to dissolve. It is hard to think of another major club in the country which would put up with serial underachievement – even when perpetrated by an iconic manager – to the extent Arsenal have. The club has repeatedly accommodated Wenger and indulged him, brushed off the complaints and frustration from the growing number of fans unhappy or angered by Arsenal's dislocation from the league and Champions League contenders. For eight years they have stuck with him through thin and thin.
The evidence of decline is inarguable. Since winning the league in 2004 they have finished behind the leaders by 12, 14, 21, 4, 18, 11, 12 and 19 points. Currently they are 21 points adrift of the club with whom they used to exchange championships, Manchester United. Best in the country? The table shows Arsenal aren't even first or second in London. Chelsea and Tottenham – whom they face at White Hart Lane in 10 days – look down on them.
Even worse, Wenger sounds accepting of their fall. "The first trophy is to finish in the top four," he said this time last year, equating qualification for the Champions League with a significant honour. Imagine Sir Alex Ferguson being allowed to get away with that year after year? Imagine Abramovich's reaction if his manager said as much?
The fundamentals at Arsenal are solid. Debts amassed by building The Emirates Stadium are being paid off at the rate of £20m per year and Arsenal can cope with that. New kit and shirt sponsorship deals with Nike and Emirates – coupled with broadcasting income – should mean Arsenal reach a turnover of £300m by 2014. They should be competing and winning.
'The Professor' achieved remarkable things with Arsenal. His commitment to diet, nutrition and sports science – now commonplace in English football – was considered revolutionary in the mid-1990s. In his first nine years he won the league in 1998, 2002 and 2004 and the FA Cup in 1998, 2002, 2003 and 2005. In 2006, he took them to the Champions League final. His 2003/04 team powered through an entire league season without losing. The team went down in history as "The Invincibles" but that's the problem with Wenger now: all the warmth and excitement belongs in the past rather than the future. He remains the Arsenal manager on the basis of blind faith and the enormous goodwill he built up in his exceptional first few years. But the point has been reached at which it appears sentiment, even softness, has replaced cold decision-making within Arsenal.
Signings such as Olivier Giroud, Gervinho, Andre Santos and Per Mertesacker suggest Wenger has lost his eye for a player, which is the last thing Arsenal need when they are prepared to make £70m available for signings this summer. Any great player they might want would inevitably look at the last few seasons and reckon he wasn't coming to a club geared towards winning things. Robin van Persie, Cesc Fabregas and Samir Nasri left for the same reason. Jack Wilshere might eventually start to feel the same way.
Arsenal need to be hauled out of the slow lane and reinvigorated. The time has come for the club to make a statement. They need to let their supporters – and everyone else – know that being skittled out of the cups by Bradford City and Blackburn Rovers is not acceptable when the club is being mocked for going so long without a trophy. They need to underline that losing 3-1 at home to Bayern Munich in the last 16 of the Champions League – with the possibility of an embarrassing aggregate defeat if they also lose heavily in Europe – won't simply be explained away.
Imagine how more seriously the club would be taken if Jose Mourinho was to arrive this summer. Imagine how much more intriguing they would be if David Moyes was allowed to take over. Arsenal are too big, too rich and powerful, to cling to a manager out of gratitude for the joy he brought them years ago. Comparisons are being drawn with how Nottingham Forest suffered because they did not have the heart to sack Brian Clough.
Wenger appears to feel himself inextricably bound to Arsenal – he is 63 now and was only 47 when he joined the club – but there is no reason why he could not go on to work at Manchester City, Chelsea, Real Madrid, Barcelona or pretty much any other great club. What's more, the stimulation and thrill of proving himself somewhere else may bring out the old Wenger. As things stand, he has been the architect of Arsenal's rise and their fall.