Sherlock is that rare beast: a TV series that understands the virtues of a "less is more" approach. Consider how many of your favourite shows ran for four or five seasons of 20 episodes, and how many of those series never dipped in quality. Even The Sopranos had its rough patches. But by limiting itself to a series every two years and with just three episodes each go around, Sherlock has encased itself in a bulletproof quality guarantee.
Which is great, but how long can the series really go on, considering the pressures of exec producer Steven Moffat being a dual showrunner, and the nature of its lead star being a genuine Hollywood A-lister? With that in mind, here are four reasons why the fifth season of Sherlock - remember, it's season 4 shooting and airing in 2016, with the fifth already confirmed by the BBC - will be the show's last.
1. Moffat's insane schedule
It's no secret that with its two biggest international series jostling for the time of their shared showrunner Steven Moffat, the BBC will have to rest either Doctor Who or Sherlock in future. The obvious solution for next year is to rest Who, what with Sherlock having been off air so long and the Timelord's recent adventures drawing record low same-day ratings of sub-4 million (in its defence, Who does great numbers on timeshift) - and that's exactly what the Beeb is doing, with no new series next year, just a bunch of specials. This gives Moffat the time he needs to focus on Sherlock, which is all but guaranteed to draw much bigger ratings.
But we can reasonably expect the situation to switch in 2017, with a full series of Who and nothing at all from Sherlock, other than perhaps a Christmas Special. The bottom line is that something has to give. Moffat, having been with Who a pretty long time already, might well step down to focus solely on Sherlock and other projects. But there's also the considerable problem of...
2. Benedict Cumberbatch, Hollywood A-lister
It's a good time to be Benedict Cumberbatch. Since his Oscar nomination for The Imitation Game at this year's ceremony, he's gone on to receive critical raves for his ongoing performance as Hamlet at London's Barbican, tickets for which sold out faster than you can say "wet knickers" and subsequently sold for hundreds of dollars apiece on eBay. In the last five years he's recorded five radio plays, narrated three documentaries, voiced two Simpsons characters and starred in six movies, and in 2016 he'll turn his disgustingly talented hand at Richard III in season 2 of the BBC's Hollow Crown historical epic. And as if all that wasn't enough, he's also bringing Shere Khan to life in Disney's Jungle Book: Origins.
A "season" of Sherlock, if you can call it that, requires a two to three month gap in the schedules of Cumberbatch and Martin Freeman, and right now that's simply not something one of the world's most in-demand actors is able to find, unless he can also manipulate time. And really, would you put it past him?
3. The forecast is cloudy for the BBC
With the current Conservative government doing their best to destroy the BBC for no reason other than their absolute disrespect for its grand history and the many millions of people who watch it daily, it's hard to predict the future of the Beeb. A review being carried out by clueless ministers looks set to implement some changes, among which are certain to be a reduction of the license fee, meaning less money for original content like Who, Luther and Sherlock. The worst part? British voters have nobody to blame but themselves.
4. Always leave them wanting more
Desmond Llewelyn's legendary Q said it best to Bond when he bowed out in The World is Not Enough: "Always have an escape plan."
Okay, so I don't want Sherlock to disappear into a hole in the floor, but the point is that so few series have the opportunity to go out on a genuine high - most reach saturation point long before they conclude - that by doing so Sherlock will cement its place as one of the great series of the 21st century. And it's not to say it can't ever come back - 5 or 10 years down the line, an older incarnation of the character could make a grand comeback, and there will be genuine appetite for it. It's not as if they don't have enough source material to work from, either.
But in the short-term, and after at least 8 years on air once season 5 is done, Sherlock should leave the audience wanting more, a mantra Luther has lived by with just three seasons to date and a fourth (with a whole two episodes!) coming later this year.
Credit to alicexz on deviantart for the killer header visual.
What's your take? Does Sherlock have another decade on air to look forward to, or will it wrap up after season 5? Share your thoughts in the comments!