I've left beers in the primary for 2 months with no ill effects, I believe some have gone longer. It will be fine as long as your temps are stable and don't go much over 70*F after the initial active fermentation period.
I think the big concern was yeast autolysis, but that was more of a concern back in the 80's when the yeast viability was not as good. The yeasts available now are healthier, and people have more knowledge about best practices, so you really can't tell the difference between a long primary, and a primary with secondary.
Look around on HBT for threads titled primary vs. secondary. It seems like any difference between the methods in end product are debatable.
Because the difference between the two methods are so hotly debated, it seems to me they don't produce a significant or pronounced impact on the final result. If they did, it wouldn't really be up for debate, most people would be like "Hells ya! It's night and day!" IMO
I have experienced autolysis, but that was from letting my fermentors get too hot, and not from the time in the primary.
Lng story short, I think it will be fine.