Do I need to add yeast before I bottle

I recently brewed a Belgian Tripel (Extract Brew) from a Northern Brewer kit. The instructions suggest leaving in the secondary 2 months. I just read something about needing to add fresh yeast prior to bottling if leaving in the secondary over 4 weeks, but the instructions from Northern Brewer did not suggest doing this.

I am wondering if I should add fresh yeast prior to bottling and if so how much would I add?

Your mileage may vary, but I've had no problems with a few big beers bulk aging for 3 months before bottling. There was still enough yeast available to do the job. It is true that over time, the yeast compact tightly to the bottom of the vessel and their viability is reduced, but there's no exact cutoff for when this happens and you need to add more yeast to naturally carb in the bottle.

I'd say if you're only going a few months before bottling you should be fine and you can always add some yeast later if you find they aren't carbing up.

Totally agree w/ marubozo. You don't need to add yeast, but some people do....

One of the seminars I attended at NHC was on bottle conditioning. The presenter cited 2 or 3 different Belgian studies that showed a blind taste preference for beers that had yeast added at bottling. She suggested along the lines of 1/4tsp of dry yeast per 5 gallon batch. This surprised me since I was definitely in the camp of "There's enough yeast in suspension, just bottle", but I'll be doing this for all bottle-conditioned beers now.

With all of that said, you could certainly bottle without adding yeast and it will be fine. I've aged beers for several months and bottled with no issues.

I think a big thing to consider is the health of the yeast after fermentation. Whats the alcohol percentage in the beer, where does it lay within the yeast's alcohol tolerance, how well does the specific yeast strain flocculate, did you supply the yeast with enough oxygen and pitch enough for them to ferment unstressed?