Carpet Seams

[bdcool]

I am putting new carpet in a place we just bought. Most of the rooms have a minimum dimension of 13'. The berber carpet my wife likes only comes in a 12' roll. Can an experienced carpet layer seam this together without the seam showing or becoming frayed in the near future? Should I go to a 15' wide carpet if a noticeable seam would bother me?
Will a higher weight (better?) pad make a difference in the quality of the job?