Originally Posted by Katsunami
You have jailbreaked and modded your Kindle, if I recall correctly. Therefore, you cannot immediately blame this problem on the device; my Kindle has never crashed and never needed to be restarted during normal use.
Jailbreaking will not cause crashes -- all it does is adds a digital signature and and modifies a couple of files not touched except at upgrade time.
I have had spontaneous reboots and have had it request reboots, mostly (as far as I can see from post facto log analysis) due to the thing running out of memory due to (I guess) kernel and cvm heap fragmentation over many weeks of use. While the kernel can move some memory around to ameliorate this, it can't solve it completely due to some regions having pointers into them that cannot be located and altered by the compactor, and cvm can't defragment its underlying C heap either (though the Java heap on top of it is, of course, routinely defragmented as part of garbage collection). Bah, when I started with Linux on an 8Mb 486 it never ran out of memory, while the Kindle has a whole 256Mb! (Of course, it had a hard disk and swap, neither of which the Kindle has to play with.)