My third Sprint Touch Diamond runs a lot cooler

[2kmy477]

To make my long story short,this is my third Sprint Touch Diamond for the last 3 weeks for me,the first one,battery only lasted 2 hours in standby,2nd one ran hot like hell,if i stream internet radio,i had to remove the battery cover to make it ran cooler,they both have the same manufacture date of 8/15/08.The third one which I recevied 2 days ago,it runs A LOT cooler than the previous 2,they all have th same Sprint Radio & ROM versions,but the third one the manufacture date was 9/15/08,i did not make any modifications on all three,all original Sprint stuffs,any1 received their Touch Diamond recently seen it runs a lot cooler?