Well, take a look at the source code of SpriteBatch (along with it’s helpers: SpriteBatcher, and SpriteBatchItem). Each SpriteBatch instance has a unique SpriteBatcher instance which has an array of SpriteBatchItem classes.
Each SpriteBatch instance (along with its helpers) does not use much space when it’s first created but can demand more space as the batch item buffer, vertex array buffer (not a GPU VertexBuffer) and index array buffer grow to meet the demand of many SpriteBatch.Draw calls. Currently, there is an upper limit of 5461 ((int)(short.MaxValue / 6)) for how many SpriteBatchItem classes can be created per SpriteBatcher instance. As the SpriteBatchItem array grows, the vertices and indices array also grow to match where each SpriteBatchItem takes 4 vertices and 6 indices. So the maximum number of VertexPositionColorTexture vertices and short indices is 21844 and 32766 respectively. The minimum number of vertices and indices is 1024 and 1536 respectively. Don’t forget that the array of SpriteBatchItem takes space and each SpriteBatchItem class as well. So all in all, I wouldn’t recommend creating new SpriteBatch instances willy nilly, and definitely not every frame, but it doesn’t hurt to have a couple of instances.