Some of these are great investments because they are in a category that evolves more slowly. Others are examples where buying quality really pays off.
PrintersFirst, while it is no longer with me, I want to celebrate again my HP 4L Laser Printer. I finally retired the printer in 2008 after 14 years of great service. I wrote about its retirement here.
The HP 4L was replaced by a Dell 1320c, with a wired network connection. It has served well for 4 years now, and will hopefully continue for another 10. It was more expensive then an ink jet, but if it continues to serve it will be well worth it.
Audio/Video ReceiversI still own and actively use ever receiver I've purchased since I started college, over 18 years ago. The oldest receiver is the Pioneer VSX-D503S.
While it no longer has the features to be a primary Home Theatre Receiver, its amplifier still works great. It now powers the outdoor speakers by my patio.
It was replaced in my Home Theatre setup by a Yamaha RX-V992 in 1998.
Network Attached Storage
Finally, my ReadyNAS NV+ has been a great purchase and constant workhorse for me.
Purchased in 2007, it is relatively young compared to the previous two examples, but for a computer accessory, it is ancient.
At its base, it provides access to a set of RAID drives over the network. But it also has a rich eco-system of software add-ons, and has been well maintained by ReadyNAS (now Netgear). With SSH access, it is really a small linux box, which in addition to providing file hosting also serves as my DynDNS client, linux shell access, SVN server, and occasional Bit Torrent client. At the time it replaced a full 'desktop' linux server, and I've never looked back. While I did have to replace the power supply last year, it has worked flawlessly otherwise, and I'm happy to upgrade a power supply every 4 years if it keeps working great.
Keys To Longevity
What are the keys to finding great electronic investments? First, the Printer and A/V Receiver categories are places where the core technology isn't evolving that quickly. In areas like these, I think it makes sense to spend the additional money up front for a quality, 'top of the line' product that will last. If you buy 'as much receiver as you can afford', it will likely last you a long time.
Second, you need to be willing to augment them with accessories. While my receiver has several digital inputs, it didn't always have the right mix. I had to add a $30 Optical to Coax digital audio convert to connect up a new component. But a $30 accessory to keep a (original cost) $999 receiver working is a no-brainer.
For my Dell 1320c printer, it has wired internet but no wireless. But again, with the purchase of a wireless adapter, I was able to extend the life of the printer.
Third, flexibility extends a components life. By purchasing a receiver with a lot of inputs, it was able to continue to provide value over time. With the ReadyNAS NV+, I was able to evolve the features it provided, reducing the need to 'upgrade' to something newer.
And finally, buy quality. At the time, there were less expensive options for each of these purchases. But buy spending a bit more for a workhorse device, I saved money in the long run.