its valid for 6 months only from the date of issue, within this 6 months you can ask them to reissue the nomination in case something happens in your PR application. once you passed the 6 months, they wont reissue nomination.
Source: BCpnp
letter of employment is also known as verification of employment letter(search google for letter format). Employment records could be T4 pays stubs anthing that can prove your work experience.. Good Luck
Re: PNP EE Applications July August AOR 2015-- Lets chat here and share timelines
ya , processing slowed down eventually.. applied on july 20 , no news so far
same here, my cic updated yesterday but no visible changes, after couple of hours i received email that your application has updated, again no changes at all.....