Sliding & Falling Merge

In the game, you can click on the sliding block, the block will move in the sliding direction, and fall physically, when it touches the block of the same number,

They will be merged into a block with a larger value, and every time you do one, all the blocks will move up, and you need to eliminate all the blocks before they reach the top.

How long can you hold on, and what big numbers can you combine? Come challenge.