I like your thinking! A couple of points:

(1) we don't really know the threshold yet to be beyond repair I think. It may be 1% but may be 20%.

(2) as others noted, it's 15 years for 0.1% damage using your math.

(3) your timeline directly contradicts the article doesn't it, which suggests keeping people in ideal conditions would have a DNA half life of millions of years.

(4) it's not a given that you need to wake people up to repair DNA. Maybe you just need to bring them to 1 degree Celsius or something. Or maybe nanobots can work on you while completely frozen. I think we are quite far from knowing right now.

So yes, for long term travel DNA repair will be important but how it actually works I think we know little about.