Number of pages for a Cover-letter to apply to postdoc position A friend and I are arguing about the number of pages needed for a coverletter, to apply to postdoc in electro-engineering.

Usually, the postdoc offer (what I called a job offer) says up to 3 pages.

My friend fills the 3 pages for the coverletter. 

To me, he should stick to one page , presenting himself, his work and why he is the most qualified for this position like any regular jobs actually.

I feel I'm right but as I do not have much experiences applying to postdocs, I cannot validate my claim.

Any insights are more than welcomed.
Please follow the link. Everything is properly mentioned as follows.
http://www.nature.com/scitable/ebooks/english-communication-for-scientists-14053993/118520525#headerAndCitation

The structure of a letter written for an entry-level position will differ from the structure of a letter written by a master's or Ph.D.-level researcher.
Typically, a more advanced position will require a lengthier cover letter.
In all cases, however, remember that your readers are extremely busy. Therefore, keep your letters from extending beyond two pages, unless the job advertisement specifically requests more details about research or work experience.