What if you didn't document tax loss carryforward every year ?

Friend had a large LT capital loss in 2006. Used some of the loss in 2007. Never used or needed the remaining loss since then.

Now he will have a capital gain this year - and wants to use 2006 loss remaining. Reading Schedule D instructions, appears the loss can be carried forward indefinitely. 

QUESTION: He made no documentation of the "available carry forward" on 2008 through 2014 tax returns (because wasn't needed).

Is this a problem ? I'm not sure if there was something he should have done. The Schedule D instructions have a "Capital Loss Carryover Worksheet" - but this says "Keep for your records". Hopefully just the old return and supporting documentation is sufficient.

I think he used Turbotax, but in 2008 did not "import info from previous year". But the old lost is there and fully documented.  Thanks !