is my hardware defective?

I have a small asic device (gridseed), Want to get more but according to cgminer, set @ a speed (conservitive) where hardware erros and rejects are rare. Increase in mh/s makes hardware and rejects increase. Tweek higher seems detrinental. The speed (megahash accepted rate) can fluctuate between 6.3m to 4.5m. That's a bit of a range. 4.5ms/s means I should turn it off and 6.3mh/s means I should give it a chance. Did I buy a lemon (?), or is that normal? Thats an wide range. Room temp is 70 F or less. Stock fan, yes I have gotton used to how loud it is, added passive heatsinks, touch anything, it's near room temp or better (to my finger). I could buy more units, but electric/benefit is questionable.
Opinions appreciated...No opinions probably means give up / shutdown.
Not looking for sprikles and ice cream, but real thoughts, including guesses on BTC in the future. True thoughts requested!

answered my own question. the hardware I prchased is flakey.

You'll find over time that the quality control on these ASICs is amazingly low. I don't know of any other industry where corporations put out products that continually fail and still make money.

When buying hardware, it's always a good idea to assume a 50% failure rate, so multiply the price by 2 when you are trying to figure out whether to mine or not. Cloud mining services take this risk of hardware failure off your back, but they have their own problems.