Indexed Search - number of indexed fields


I was wondering if there is recommendation regarding the number of business data fields that are indexed.

Is there a value after which the search does not perform so well or are there any drawbacks of having many business data fields indexed? (many= around 50)

Does anyone know what aer the benchmarks against which SAG tested the indexed search. Can one see how the search evolves based on the number of indexed fields?

What are the community recommendations:

  1. Index all the fields (from the search and results page)
  2. Index only the fields from the search page and retrieve the non-indexed ones from the results page in another matter.

Thank you for your responses/ideas.

Vlad Turian