Is it normal for the 3GS to drop wifi after being idle for 15-20min

[nkj575]

hi , first iphone here , is it normal for the iPhone 3GS to drop the wifi connection when it goes idle (ie,screen dims and locks) unlocking the screen it quickly connects back to the wifi most of the times. i tested it by finding the ip of the iphone from the router , pinging it and then waiting 15-20 mins and then pinging it back again. this fails until i unlock the iphone after which it connects again .

 

[spooned12000rpm]

Wifi switches off to conserve battery from what I've read, it suprised me too (first iPhone here too) coming from an iPod touch which stays on all the time but that's because it has no other means of outside comms for push etc

so perfectly normal

 

[nkj575]

Thanks it makes me less worried now , I thought I would have to make a apple store run and I hate doing that