For a long time, those first 72 hours at games retail were by far the most important.
How many units publishers managed to shift within those opening few days would go on to decide whether they had a hit on their hands or not. By the third week, prices would begin to erode, copies would end up in the pre-owned bins and consumers will have moved onto the next big thing.
That's why publishers hold such extravagant midnight launch events in cities around the globe, and aggressively incentivise pre-ordering - to get that Day One figure as high as possible.
Although the triple-A industry has long since moved into the 'games as a service' model, with recurring digital revenue becoming increasingly important, Day One and Week One are still being used as a barometer for how successful a game will be. That's why there's so much shock around the early sales figures for Titanfall 2 and Call of Duty: Infinite Warfare. In the UK, Titanfall 2's Week One sales were down by more than 75 percent compared to the original, whereas Infinite Warfare's launch numbers were almost half of 2015's Black Ops III.
Furthermore, Ubisoft has warned investors that pre-orders for the upcoming launch of Watch Dogs 2 have not been as high as it had expected. Perhaps that game may be the next one to have a lower-than-hoped first week.
Yet there's increasing evidence that those opening day (or week) numbers are not quite as crucial as they once were.
For this analysis I've used available GfK figures on how games have performed during their second week on sale in the UK. Do note, however, that this data does not include digital download numbers. Although the physical boxed market remains the dominant force for triple-A console releases, it is believed that console download sales are on the rise, and that should be taken into account when considering these figures.
To begin with, let's take a look at the early sales of Battlefield 1 and Titanfall 2.
EA's Battlefield 1 enjoyed a strong first week of sales compared to its predecessors Battlefield: Hardline and Battlefield 4. However, those comparisons are a bit misleading because Hardline is a spin-off and BF4 had a staggered release due to the arrivals of PS4 and Xbox One. Perhaps a more accurate comparison would be with 2011's Battlefield 3, and, unfortunately, Battlefield 3 was far more successful, selling around 40 percent more copies in its first week than this year's game managed.
However, whereas Battlefield 3 suffered significant falls of 54 percent (Week Two) and 62 percent (Week Three) during its subsequent weeks on shelves, Battlefield 1 sales have proven more resilient, with sales drops of 39 percent (Week Two) and 45 percent (Week Three).
In other words, Battlefield 1 is starting to catch-up on Battlefield 3, and after three weeks the gap between the two is now just 28 percent.
EA's other big shooter this year is Titanfall 2, and that has suffered a disappointing launch - hurt, in part perhaps, by its poor release timing. The game sold significantly fewer units than its predecessor did in its first week. However, whereas the first Titanfall (released in March 2014) endured a sales drop of 73 percent in its second week, Titanfall 2's drop was just 41 percent. It has a long way to go, but there's hope that the game may yet reach a decent audience.
It's entirely possibly, with the recent spate of games that have launched with too many bugs or online services that fail to work, that consumers are choosing to wait before spending their money. And it's a trend that began to emerge towards the end of last year. Assassin's Creed Syndicate performed poorly in its first week on sale in the UK, selling over a third fewer units than its predecessor (the criticised Assassin's Creed Unity). Yet Syndicate fought back. The game's second week sales fell just 39 percent (versus 62 percent for Unity) and after six months Syndicate had reduced the gap on its predecessor (although it has yet to overtake it).
A similar thing happened with Call of Duty in the UK. 2014's Advanced Warfare sold 780,000 boxed games in its first week on sale, whereas 2015's Black Ops III managed only 670,000. Yet, whereas Advanced Warfare fell away quickly, Black Ops III did not, and after a year on shelves, Black Ops III is now trending ahead of Advanced Warfare.
There are other recent examples of games that have enjoyed a strong long tail, such as the recent Doom, however, there are exceptions. Take Fallout 4, for instance, which had a huge first week at retail, but sales fell by 80 percent in its second week.
Day One and Week One is therefore clearly still very important. Even if sales do pick up for Call of Duty: Infinite Warfare and Titanfall 2, both games will be hard-pressed to surpass their predecessors now.
"Even if sales do pick up for Infinite Warfare and Titanfall 2, both games will be hard-pressed to surpass their predecessors."
Yet what we've seen at retail over the last 12 months suggests that a bad Week One does not mean it's all over for these products.
I'll leave you with this final example. Rainbow Six Siege launched last December to little fanfare, with Ubisoft cutting back its PR and marketing activity in the wake of the November Paris attacks. Its UK launch sales were small, and actually only a little better than what Titanfall 2 has managed to do so far.
Yet over the course of the last 11 months, that game has emerged as a real success story in the UK and around the world - Ubisoft now says it has over 10m registered users globally, which was unthinkable a little under a year ago.
Ubisoft supported that title with regular DLC, and was rewarded with positive word-of-mouth, which in turn inspired both YouTubers and specialist media to cover the game for months and months after launch.
It is the shining example that even if Titanfall 2 and Call of Duty: Infinite Warfare struggle to live up to the commercial performance of their previous games, they may well still lead a long and profitable life.