i don't know how messages.0, messages.1 , .2, .3 has created. System is up at least for last one and half months. So, those dates should not be match with reboots. If you see messages.0,1,2,3 size has not changed. Only "messages" size has changed. I m not sure Is only for file 'messages'- the size of /var is increasing?? Or else something hidden.
Could u pls tell me about something 'log rolling'??