I've never noticed the hop presence weakining in any of the beers I've extended primaried. If one is making an IPA and dryhopping in primary, I've never found it noticable even in there.
Sinnick, many of us purposefully leave our beers in primary for a month or more, rather than secondarying. People have left their beer in primary for a year with no issues. I've done nearly that. This discussion has been thoroughly covered in this thread, it's become the "uber discussion" on this topic.
To Secondary or Not? John Palmer and Jamil Zainasheff Weigh In .
Need to clarify something though......Fermentation time is only as long as the yeast are converting sugars into alcohol, and that only lasts a week, maybe two at the most, anything after that is considered conditioning.