^ 67.9 is for the case part of the CPU that most programs don't monitor.
Go by core temps...the i7 920 cores throttles near 100'C.
90s'C is severe degradation, upper 80s'C will cause minor degradation, mid 80s'C is fine for overclocked benchmarking, lower 80s'C is fine for full load overclocked, and it's generally advisable to keep it under 80s'C for general 24/7 use.
When you say average, what are you going by?
1. HWMonitor, which will monitor your core temperatures
2. Prime95, which is a program that will test your computer at full load (100% load)
Idle temperatures for the i7 920 range from 30s'C to mid 40s'C depending on the ambient, and full load temp for the i7 920 stock with a V8 is usually high 50s'C to low 60s'C from what I've seen.
But what is your ambient (room) temp? If your ambient is 60F then 50C idle temps are huge for a non-stock cooler (mine is stock). If your ambient temp is 90F then 50C isn't all that bad. Load temps are more important though.