Well here is a nifty table that gives you some ideas.

 

Full

Incremental

Incremental (inc)

Adaptive

HTTP 3xx error

Never

never

never

never

HTTP 4xx error

Immediate

Immediate

Immediate

Immediate

HTTP 5xx error

Never

Never

Never

Never

SPS page removed

3rd crawl

Never

Immediate

Never

STS page removed

3rd crawl

never

immediate

Never

Rule to exclude

Immediate

Immediate

Immediate

Immediate

CS removed

Immediate

Immediate

Immediate

immediate

Unvisited URL in index

3rd crawl

never

never

never