My twins are now 1.5 years old. Their combined weight is 50 lbs. Together with the twins trolley will be over 70 lbs. It has become very heavy and quite dangerous for using in the escalator. So I seldom use it now. Only use it for going to Disneyland.
Now I usually use one single trolley and the other baby being carried by Dad or the maid. Cause they now can walk and explore and feel bored and don't like to stay in the trolley for long.