Do u think jailbreak affect the performance and battery life of idivices ?!
Not in my experience. I successfully ran an iPad1 jail broken for about a year with no noticeable slowdown or battery problems. The only reason I don't still have it jail broken is that I put iOS 5.1 on it and gave it to my sister (because I have the new iPad
).
I also am running an iPhone 4S that has been jail broken (iOS 5.0.1) since the jail break was released. Again, I have not noticed any slowdowns or battery issues. But, then again, you could get battery drain if you run tweaks (like a weather app that constantly refreshes) that ask more of the battery or processor. But, it would be your decision to accept that draining - it doesn't happen normally. As far as I can tell, my phone is no slower than it was when it was stock. Of course, this is one person's anecdote - so it doesn't make it ironclad. But, I've never had a jail break issue that I did not cause myself. Given the opportunity, I'll choose jail break every time.
And yes, having a jail broken iDevice will void your warranty - but ONLY if you attempt to get help from Apple with the jail break installed. If you restore the iDevice to stock, all traces of the jail break will be gone. Then, they'll never know the iDevice was jail broken. Restoring to stock is a very simple process...
Hope this helps and clarifies.
Marilyn
P.S. And, since you're asking questions about jail breaking, I'm going to move this post over to the Hacking section of this forum. There (here?), others with jail break experience can see it and chime in...