No, it shouldn't. For Cat6 the most likely cause of poor transmission is not the cable length (unless we are talking about 100m+), it is the integrity of the connections. It is very difficult to get a perfect crimp on those connections, and you basically need very expensive hardware to ensure you got it.
I never recommend people to do cat6 in their homes, cat5e is soo much easier and you still get comparable speed. The chances of you doing a perfect crimp with hand tools on cat6 are 3-5%.