Nothing wrong with going to sleep early if it results in your
waking up the following morning after a reasonable amount of
sleep feeling refreshed.
Now, if you knock off at, say, 9 p.m., get up at 7 a.m. and
still feel cruddy, then you should be worried. 
i slept at 8.45 last night, woke up at 5+am 
then i made myself go back to sleep and woke up at 9+
but... i don't have any reason to sleep so early.
the timings i sleep and wake up are like an old man who has to
get up before sunrise for taichi.
