Thoughts on Not Carbonating After Months

I brewed a Belgian tripel about four months ago and pitched a rather large starter of healthy yeast - I think it was a White Labs 530, but I don't have the details handy. Fermentation raged like it always does with that particular strain and I didn't think anything about it - I don't have a fermentation chamber yet, but this was over the winter and the temperature of the surrounding area doesn't exceed 65 deg. I let it sit on the yeast for two months, more or less as an experiment to show that long primaries weren't harmful, and then bottled it with some priming sugar based on the volume of CO2 appropriate for that style. After 3 weeks at 70 deg or so, it still hadn't carbonated at all. So, I tasted one every couple weeks after and didn't see anything happen, so I put it in boxes, moved it into my basement, and pretty much have forgotten about it for the past 3 months.

I'm planning to let it sit for a while until I even think about checking it, but I'd like to hear the communities thoughts on this. Is it possible that two months on the yeast cake pulled all the yeast out of suspension and there were simply no yeast left behind to carbonate the beer? I've read about a lot of brewers that have had more time on the yeast than I did and not having problems - anyone see a potential mistake I might have made here?

Is it still sweet, like the priming sugar never got eaten?

Tripels are pretty heavy beers... it is possible that your yeast ran out of gas and couldn't ferment any more. If this is the case, the first thing I would try is moving a few bottles to somewhere hot -- like 80 degrees or so. Maybe shake them up a little bit too. That usually gets the yeast going.

Otherwise, I've heard of using a second strain of yeast to carbonate the bottled beer, that might work if added to the bottles in an emergency. I never did this, but I am sure someone here would know of a good one to try.

I've had high gravity beers take 3 months to properly carbonate. I would check one now and if there still not carbonated then you'll have to figure out a way to add yeast now that there are bottled.