Power conditioner -- when to replace?


I just bought a Furman power conditioner for my bedroom system to manage all my cords.  While investigating power conditioners, I came up on a couple of sites that suggested that they lose their effectiveness after as little as two years.  I have a beefy PowerVar 12 Power Conditioner that I have had in my main system  for maybe 10 years and I got to thinking that it might be at the end of its life.  

I welcome any thoughts on this longevity issue.  Thanks. 
whitestix
I have a Monster Power on my TV/DVD system that is over 20 years and hasn't been off in years ,
Wow. what a story. "lose there effectiveness??                
My Furman is at least 12 years old. I bought  it used nine years ago.I also bought a used PS Audio P-600 then too.Still in use. still work great.  
Now there IS one small part which DOES stop working. and that is the overvoltage surge protection,(If the power conditioner has this?)  if they are a the MOV type which fail if they get put to use. So generally those would be no good after a few years in general But that does not make the power conditioner no good. just if it used those for over voltage, then they need to be replaced.     
So my guess is the op is confusing surge protection and power conditioning
Thanks for all the input, it is very helpful.  To Elizabeth's last point, the usefulness of a "power conditione" includes both functions, typically.   Frankly, it the surge protection is kaput after a period of time, then one is left with only power conditioner and no protection for their gear in the event of a voltage surge.  I think both functions are equally important.  

Question:  is there a way to discover if the surge protection is still effective in a unit? 
Sadly MOV are not easy to check if they are any good. Best bet is to just replace them. They are dirt cheap. and a whole pile are usually stuck in the spot. Just replace them and even add a few more.There ARE other kinds of surge protection. You would need to ask the maker what sort your unit has (if any)If you do not know what they look like, very distinctive blue flat disc. Google "images" MOV and you can see hundreds of them.