I have a weizenbock I brewed back in October, also around 8%. I use the BCS recipe and fermented in the low 60s with WY3068, per Jamil's suggestion. It was perfect after just 3 weeks in the bottle, and so far it's held up well to aging. I only have one bottle left, but I might drink it tonight. To be honest I don't think aging has improved it that much, though it certainly hasn't hurt it.
Sorry I can't provide a more solid answer! I know how hefes can be past their prime after they're a few months old but this hasn't shown it yet.
If you have a good recipe and can still ferment in the low 60s, you should be fine bottling 3-4 weeks before the competition. I brought mine to a homebrew club meeting after 2 weeks in the bottle and everyone loved it.