You should be OK without any extra yeast as long as you're patient. It doesn't hurt to add a little extra at bottling as an insurance policy if you'd like. But you need way less than you think you do. One or two grams of US-05 at bottling is all that you need for a 5-gallon batch. If you use too much yeast you will get a lot of trub in your bottles.
+1
When I bottle condition, usually at 70oF, an average beer takes 10-14 days. The big beers, 8-10% usually can take at least 6-8 weeks under the same conditions without adding yeast. IME, the bigger beers need the additional time anyways simply to condition and mellow, sometimes as long as 3-5 months when they really shine:)
I brewed a Belgian Quad in July for the Holidays this year, 10%, just sampled a bottle a few days ago to see how it was coming along, needs a bit more time but tasted delicious, be patient and you'll be rewarded!