Perlin Noise not working properly when using offset

I'm trying to write a shader that uses Perlin Noise. I am using the function noise with an offset that will change with time. All good so far:

 float offset = 0;
 float noise1 = noise((IN.worldPos.xz + offset)) + 0.5;
 return noise1*float3(1, 1, 1);

However, when the offset exceeds around 500 the noise doesn't work properly.

 float offset = 500;
 float noise1 = noise((IN.worldPos.xz + offset)) + 0.5;
 return noise1*float3(1, 1, 1);

Why is this? Here is the noise and hash function I am using:

         float2 hash(float2 x)
         {
             const float2 k = float2(0.3183099, 0.3678794);
             x = x*k + k.yx;
             return -1.0 + 2.0*frac(16.0 * k*frac(x.x*x.y*(x.x + x.y)));
         }
 
         float noise(in float2 p)
         {
             float2 i = floor(p);
             float2 f = frac(p);
 
             float2 u = f*f*(3.0 - 2.0*f);
 
             return lerp(lerp(dot(hash(i + float2(0.0, 0.0)), f - float2(0.0, 0.0)),
                 dot(hash(i + float2(1.0, 0.0)), f - float2(1.0, 0.0)), u.x),
                 lerp(dot(hash(i + float2(0.0, 1.0)), f - float2(0.0, 1.0)),
                     dot(hash(i + float2(1.0, 1.0)), f - float2(1.0, 1.0)), u.x), u.y);
         }