I feel safe as long as my CPU on-die temp is around 20C below AMD's max rating. This past summer with my PC room around 80F my Barton 2800+ @ 2.3GHz was peeking at 65C-67C with Prime95 stress test running, the socket temp was around 52C. As long as the systems are stable I really don't worry about it, this system is 7 months old now and it never crashes.
I use Mother Board Monitor on my Barton system since my mobo (Asus A7N8X v2) can read the CPU on-die temp on the Athlon XPs, on my older boards I just add 10 to 12C to the socket temp to get a ball park figure for the on-die temps.
On the AMD K7 cores, I've had a Slot-A, Duron, T-bird, Palomino and now a Barton, all over clocked with coolers that cost from $8 to $23. Some guys will tell you it should run at 50C or 55C max and to buy a big expensive cooler and put 6 fans in your case, etc,etc, maybe they just like spending more money on coolers and fans then the CPU itself, I never had to.
Most overclockers are thermophobes ...including myself - i just don't like high temps...but i won't scream in terror if my temps exceed 50 or even 60°C either
Generally, you don't need to worry as long as your system is stable and your temp stays below the max specified temp for your CPU. Ofcourse, having lower temps means less stress for your CPU and prolly some more overclocking-headroom, too
Having 6 case-fans is uneccessary, but a good airflow(most people have two fans, one front-intake and a rear-exhaust) will help keep system-temps down and enhance the lifetime of your components(like HDDs).
------------------------- The opinions expressed above do not represent those of Advanced Micro Devices or any of their affiliates. <center><font color=red>MODERATOR</center></font> AMD Athlon 64 X2 6000+ 89W :: Asus M2N32SLI Deluxe :: 2x1024MB Muskin XP2-6400 DDR2-800 :: BeQuiet! Darkpower Pro 530W :: 2x WD Raptor 74GB/10k rpm, RAID 0 :: ATI Radeon X1950XTX