I'm 3 years into using Ubuntu as my default OS, but I notice that Ubuntu is becoming slower after some weeks of installation. On all the Ubuntu versions I have used including "Ubuntu 10.10, 11.04, 11.10 and 12.04", the boot becomes slower. When I make a fresh install, it boots in just 17 seconds... after 2 mouths, the system takes almost 1 minute to boot (Slower than Win7). I tried to disable all the software that starts with the System, but the problem continues (I had this problem with my older notebook, so it's not hardware related).
Ubuntu's boot looks inconsistent too, because sometimes I see the purple boot screen, sometimes I just can see an underline at the left-top side of screen. So. Why is Ubuntu's boot going slower with time? Can it be fixed?