I have also asked this same question in the past, regarding a RIS that was about 9.5% ABV and had been in the fermenter for 2 months. After listening to the answers, I did NOT add any yeast at bottling, and my beer carbed fine.
It really is a matter of what you are comfortable with. There is no reason not to add yeast at bottling (other than the slight cost of more yeast). Adding extra yeast for carbonation will not hurt a thing, and can give you peace of mind that you are not wasting several gallons of good beer. If you choose not to add any yeast, there is about a 95% chance your beer will carbonate normally, and should work out just fine.
So really, what it boils down to is this... If you are worried or unsure about your yeast being healthy, buy another packet of yeast and mix it in the bottling bucket when you prime. If you are not terribly worried, then let it ride, and it is ALMOST guaranteed to be OK.
"Give a man a beer, and he will waste an hour. Teach a man to brew, and he will waste a lifetime!" Bill Owen