Taking 3 + hours to fully charged

I recently bough an iPhone X and followed the instructions to fully charge the device before using it the first time. But my iPhone X is taking longer than usual to fully charge till 100%, on an average of 3+ hrs after using it for 10 days. Is this a normal time taken for the iPhone X or should I contact my reseller on this issue? How are the other iPhone X getting fared on the battery charges.