you may have problem if your expiration date is too close

They will definitely ask you why you don't have enough time valid. If your trip is short, you may get away from it. But for example if you stayed in China for the past 2 or 3 months, then you say you don't have time, or forgot, they will take soem exception with it.

That's not the worst. The airline may not let you board the airplane in China.