How far should I overclock?

[Eidoss]

This is the GPU I have:
http://www.sapphiretech.com/presentation/product/product_index.aspx?pid=2043&lid=1
Sapphire R9 270X
Now, I know that it is factory overclocked but I've seen on various forums that some people have gone a bit farther. I'm using AMD OverDrive. My temperature while playing has never gone above 60C so there is some room for improvement.
My GPU clock was at I think 1070MHz now its 1100MHz
Memory clock was 1400MHz now its 1500MHz, I can't say I've gained a lot of FPS it is maybe 5-7 FPS but it's still something. But my question is how far can I go before... breaking it, I'm planning on using this card for 3-4 years before I buy a new one.
Also my GPU clock can go up to 1400MHz, memory clock up to 1625MHz and I have a 550W PSU.

 

[geofelt]

How much do you need a higher overclock?

My take is to not fool with a factory warranted overclock.
If the card does not perform sufficiently well. buy a stronger card.

If you want, go ahead and overclock to whatever you can, but take the time to measure your performance before and after so you can determine if it is worth it.