Lifespan of amps and preamps?

You didn't specify your source. Analog or digital? Both? Those would be the places to upgrade!

Are they totally dated, meaning past their intended lifespan from an internal component perspective?

No. But my memories a little hazy. You should check. Like in the Bruce Willis movie RED. Made before expiration dates and you're okay.

 I have to say it all still sounds really good to me.

See? Like Malkovich with the Twinkie.

 But I never really listen to other systems.

Perfect. This is the key to happiness. Avoid internet, magazines, and stores. You'll be fine.

Thanks for the responses.  I know my stuff is not truly audiophile, but I  feel like its pretty good quality.
As far as inputs, when my CD player died a few years ago I did invest in a SONOS Connect (which apparently is on its way to becoming a brick) to stream into my system.  I also still use my record player as well. 

I recently moved my office to my home (like so many) and decided I wanted sound in my new office room.  I am going hi tech.  Again, not exactly audiophile--SVS Prime Wireless bookshelves.  They have Class D amplification, are true active monitors with digital crossover, and have a built in DAC.  So all i need is a streaming source.  This is the first set of new speakers in my home since, well 1990.
Thanks again for the input on the old system.  Sounds like there is no obvious parts that expire...I do not really have the money to replace it anyway. 

The time to replace is when one of them expires and cannot be mended.

if you like what you have, and can't afford to upgrade or refurbish...but sounds like you're still curious...you might be surprised at how good some new entry level gear can sound...and gear with dried out, dead caps, can still "play" for years...