i've ramp my athlon +3200 939 to 2.5ghz... (if not only for my ram, i could have gone pass 2.5ghz) and its been like that for 9 months now... prime95 for 23 hours... no errors...
i think your +3500 could go up to as high as 3ghz, for as long as you do it correctly... and of course, with the proper cooling.