I have absolutely no doubt in my mind WHATSOEVER that this is a scam to try and force customers into buying new, black boxes. Therefore, this will happen again in the future.
Shame as I previously recommended NOW TV to everyone. Now they're on my "BT, British Gas, Vodafone" scam list.
I am surprised you think upgrading from the white Now TV box to the black one is a scam, simply because if you knew anything about computers and their peripherals you would know that most IT kit only have a useful life of two to three years.
Also, from a personal view point, I do not like how the IT world churns computer equipment, i.e. making a perfectly useful item obsolete by bringing out the next new shiny hardware. It's even worse in the software/application end of the IT industry, software makers are always bringing out new software that cannot run on older machines and so forcing the user to upgrade to something more powerful if they want to keep working.
And so, unfortunately, that's what happened to the white box, app makers, such as YouTube and the BBC, upgraded their apps until the box could no longer work properly, the apps had grown beyond what it's CPU and memory could handle efficiently.
So you see SB, that's the way of the IT world, making people idealy change their IT kit every 2 - 3 years.
As for me, I don't like the churning of equipment either, I try to keep my IT kit until it no longer works and is uneconomical to repair.
What type of NOW TV box do you have... The old white one or the newer black one?
If you have one of the old 'white' boxes and are exclusively using it to access third-party apps such as BBC iPlayer, ITV Hub, All 4, Demand 5, RedBull TV, YouTube etc, you could try deleting any non used apps and/or resetting your old 'white' box to free up memory.
However, if the problem persits you're better off treating yourself to one of the newer 'black' NOW TV boxes.
And just-so-you-know... NOW TV have no control over 'third-party' apps. Their content, their delivery systems, their UI's and their distribution platform are entirely controlled by the service provider.
If you read my post, which is about 5 or 6 posts above yours, you will see that no matter what digital streaming device you buy it will only last 2 - 3 years, that's just the way the IT world rolls.
Please note, if you want examples of churning that's readily available look at how many models of Apple iPhones are released every year, or any other huge consumer brand of computer based items.
However, as a savvy customer you are free to choose your own way.