You will hear mixed opinions on this, i have a 1600 degree pyrometer and try to keep it under 1400 at full throttle, i would say try not to run it at above 1100 for more than a minute or so. Your temps shouldn't get that high unless your under heavy throttle or towing hard. From what i hear, it's ok to run it up to 1500 ish if your not gonna hold it there.
I have an alarm set to chime at 1350... I've also heard that you don't wanna go over 1500 for long. You'll see higher temps with restrictive exhaust. I've heard that the new downpipes that are coming out for the LB7's are dropping the EGT's... couple that with new up-pipes and manifolds and your EGT's can drop significantly... naturally, you wanna get rid of the stock exhaust system. If you change out the up and downpipes and still have EGT probs... look at a bigger intercooler.
on my #5 setting ive hit 1650 on my 2000 degree gauge going up a steep ass hill thats like 2 km long racing a mustang only for a few seconds then i saw the gauge and let off immediatly and the stang went flying by hahaha