Helping people with computers... one answer at a time.
Windows has what's called a 'lifecycle' - a series of stages beginning with release. I'll review what happens as a version of Windows nears end-of-life.
My OS is Vista and Microsoft intends to stop support on 10-Apr-2012. I know that thousands (if not many more) people throughout the world are very concerned about this. I personally am now very pleased with Vista. I have tested it against other computers running XP and Windows 7 and found that in all cases, it compared more than favorably. This is in no small way due to your newsletters as by using image backups, I have been able to modify Vista considerably. Your advice in this matter would I know be gratefully received by many people, especially those on tight budgets.
While I've rarely heard of this concern about Windows Vista, the sentiment actually applies across all versions of Windows.
How long can you keep using it?
Well, the glib answer is: as long as you want, as long as you understand the risks.
The more practical answer is: a lot longer than you may think.
Just ask the millions still using Windows XP.
Windows versions go through various stages over time, referred to as the product lifecycle.
From initial sales through end of sales through a couple of different stages of end of support, every version of Windows lives, and dies, through a fairly well-defined series of stages.
Let's look at each of the end-of-life stages individually.
At some point, each version of Windows stops being sold. Typically, this happens after the next version has been available for a while. Even then, there are two different dates, depending on what kind of Windows edition you're talking about:
Retail editions: These are the copies of Windows that you can buy directly in computer stores and via online vendors. They're typically "generic" in that they don't assume any specific PC.
OEM editions: These are the copies of Windows that are included pre-installed on new machines. OEMs are companies like Dell or Gateway that sell actual computers. The version of Windows pre-installed on a computer is typically configured specifically for that manufacturer.
Retail sales stop first and OEMs are allowed to sell their pre-installed versions of Windows for a longer time - a year or perhaps even two longer.
There's nothing at all wrong with running a version of Windows that's recently gone off the market. It's sort of like purchasing last year's automobile model. Support will continue for some significant period of time.
This is what you're looking at with Windows Vista: mainstream support ends on the 10th of April, 2012.
Note that regardless of operating system, the end of mainstream support assumes that you have the latest service pack. In Vista's case, that's SP2. Mainstream support for Vista with only SP1 actually ended last year.
So what do you lose after mainstream support ends?
To be honest, not a lot that really matters:
"No-charge" incident support - I believe that these are those cases where you call Microsoft for support and that support turns out to be free, by whatever policies Microsoft might have in place. Most commonly, I think this is the case where you pay an up front fee which is refunded if the issue turns out to be due to a problem in Windows itself.
Warranty claims - The ability to make a claim for a refund relating to Windows own product warranty ends.
Design changes and feature requests - The ability to submit requests for product changes in this version of Windows is terminated.
To be honest, none of those really matter for most people. In fact, I'd wager that they're things that most people didn't even know of and they're more commonly made available to corporate customers.
The important stuff doesn't really end until the next level of end of life.
To put this in perspective, Windows XP has not reached this date yet. It's not until 2014 for XP and 2017 for Windows Vista.
The end of extended support is where you lose something important:
If you continue to use your version of Windows beyond the end of its extended support, you run the risk that a vulnerability might be discovered and not fixed.
Once extended support has ended, Microsoft pretty much washes its hands of that version of the OS. The online knowledge base of support information remains available, but that's about it.
Now to be fair, Windows XP will have been supported to this level for over 12 years and Windows Vista for just over 10. It's very likely that requirements of software being produced at the end of those periods will almost necessitate moving to newer version of Windows anyway, if not newer computer models as well.
But, let's say that you want to keep running your Windows Vista beyond 2017 anyway.
Understand the risks of not getting security updates, but as long as you have hardware that it supports (like the machine it's on now), it'll still run. End of support doesn't mean you can't keep using it.
Just ask those people who are still running Windows 98.
You might be at risk for malware or other security related issues. But on the other hand, malware will more likely also target the more current, and presumably more popular, eventual successors to Windows. As part of a dwindling minority of Windows Vista users five or more years from now, you might not present that interesting a target.
Once again, just ask those folks still running Windows 98.
More practical matters will probably force the issue.
A software update may require more than your current version of Windows can offer.
New software that you want to run might require a newer version of Windows than the one you're running.
Should you ever need to replace your computer or some peripheral, it's possible that newer hardware may not be supported by your older Windows version.
In your case, for Windows Vista specifically, I see no problem continuing to use it well into 2017 if you're happy with it.