Contrary to popular delusion, NVIDIA is not on a six-month product cycle, at least if you take new product to mean new GPU.
NV10 to NV15 = ~ 1 year
NV15 to NV20 = ~ 1 year
NV20 to NV25 = ~ 1 year
NV25 to NV30 = ~ 1 year
In between (~6 months) we get the "refreshes," which have never been a different core. There was the GeForce256 DDR (NV11), GF2 Ultra/Pro (NV16), GF3 Ti (NV20-Ti) and the GFX??? (NV28). The only one that is even slightly different is the NV28, and that is only to add AGP 8X.
Anyone who expects the NV35 to be out any sooner than late 2003 is deluding themselves.