In this case, I think it is a jury's finding of fact re: the statute of limitations. Unless the appellate court finds that the trial court and jury is clearly erroneous, it will usually give significant deference to that finding.

It's even harder than "clearly erroneous" (the standard applied when a judge makes fact findings without a jury). Under the Seventh Amendment, if a hypothetical reasonable jury could have reached the result that the actual jury did, then that's the ball game [0], even if the trial judge or appellate-court judges would have reached a different result.

[0] Assuming that the trial judge didn't materially screw up in admitting or excluding evidence, or in instructing the jury about the law, and also assuming no proof of juror bias or improper influence.