I've only had Cubes running overclocked for two or three weeks, but no issues past a single X'd card - just haven't had time to fix it. About half my cards have actually been jacked to a higher-than-factory overclock just because.

I have a Blade that's been in continual operation at 20% faster than these Cubes' overclock frequency, for two months without a single issue. The way I figure, as long as you keep them cool enough, they should last their expected (profitable) lifetime.

Also, effin' YES on the DDWRT. My last two wireless routers were both flashed to said firmware, and I have another running around which needs to be given "the treatment".