End of the month syndrome is unfortunately familiar common in manufacturing businesses: a large portion of the monthly shipments happen in the final days of the month. It's not because customers don't want the products earlier, but because they are driven by competing needs. On the one hand, they want to keep costs under control which might mean less overtime and lower pressure to get products out the door. But then there is also the need to meet customer needs and meet the demands of business to show consistent bookings each month (we don't get paid until we ship). This often drives a different set of behaviors - do whatever it takes, including overtime or other "expensive" measures. Similar effects happen in supply chain and retail -- often driven by similar thinking (discounts to drive unit sales, even though they don't drive profit).
Of course this kind of thing can happen on other cycles: end-of-quarter or even end-of-year. Here is a great example of this phenomenon from today's Wall Street Journal: Airbus Tackles Its Procrastination Problem: says
Plane maker had to work round-the-clock the past two Decembers to meet yearly jet-delivery targets
Reading the article further, it isn't just the last two Decembers - it has been several years where they've had to significantly push production in the last year of the month to hit the numbers. And even more evidence of the syndrome is that production is much lower in January and the first quarter of the year than towards the end of the year. The article also makes it clear that there is a business need to be more predictable: shipping consistently each month, rather than the big ramp at the end of the year.
How to overcome the problem? The general direction is to find a solution that allows companies to meet the needs of spending wisely AND shipping on time.