Some 2007 models have had issues with the big end bearing on the crank failing. However, that was 13 years ago, so unless its an ultra low mile example, if you had a problem, you'd already know it. If you just keep the oil clean, with a quality oil, you shouldnt have an issue.
There is a chart on BWB that people were using to register the crank failures.
There are about 40-45 entries on the chart, and about 15 failures. Doing quick math shows there were almost 10,000 XB12's produced in 2007. If there were 100 failures, it would barely be 1%.
The 2008+ models were much more robust with the larger crankpin and better rods, which is why Mike Lowary used one for his 1170.
If you did have a problem, just send the crank to Darkhorse and they can rebuilt your stock crank to better than new.
I wouldnt lose sleep over it.... plus there are so many other things to go wrong. Look at my bike.... the top end got so hot, it basically ruined the crank in the process. Last night I noticed the rods on go from a golden brown color to black as they get towards the small end.
Also, if you do decide to sell, hopefully for you the potential buyer doesnt see this post. If I was shopping for a 2007, this would seriously devalue what the bike is worth. The reality is that all the bad cranks should have revealed themselves long ago. Even if your crank did fail, is it because its a bad crank... or just because its 13+ years old?