A few comments on the wordings in your post which might look subtle but they hold the essence of EEA regulations.
Agreed with Punjab , but as I recall , back in the days the UKBA always insisted on applications made 4-6 months prior to the expiration of the visa , That's what we did when we applied for the 5 yr visa and for the permanent residence.
You are mixing UK immigration rules with EEA regulations. Under EEA regulations, there is no "visa". The 5 years Residence Card is just a
confirmation by the HO of your rights as a family member of EEA national exercising treaty rights. You are not required to apply for one and as such the "visa" doesn't "expire". As a matter of fact, you don't even need to fill in an application form and still your application needs to be considered.
We received our PR's before the 5 yr was completed , lets say 2 weeks before it was about to expire.
Unlike UK immigration visa categories, you don't need to apply for PR before the RC "expires". You can apply any time you wish, before or after the date on the RC sticker as long as this is after 5 years of exercising treaty rights. As mentioned before, your PR was issued because you have been in the UK for more than 5 years under the EEA regulations. It has nothing to do with the 5 years on the sticker.
In relation to the amount of documents , it clearly states in the application to provide as many documents as possible, so if the UKBA wants it then why not and as my logic tells me , the more documents the better.
Could you point out where does it say in the application to provide as many documents as possible? It lists several documents, that's true, but they are only listed as examples not requirements.