How long does it usually take to erase cache? While in bootloader, I connected a USB cacble and ran this command to erase cache:

#&gt; fastboot flash cache cache.img 
target reported max download size of 1073741824 bytes
erasing 'cache'...


PROBLEM: It has been running for 10 minutes already. The phone's screen still says erasing....
The cache.img is 14 MB, downloaded from Google.

Should I give up?
About how long does it usually take? A few seconds, a few minutes, a few hours?
Why flash cache? Just erase or format would be enough.

Comment made me curious - care to share for what reason erase is unusable?

Either way it should only take a few seconds. Try flashing some other partitions (ones that won't touch your data, of course) and see if they pass.