The 2 forks used together are to match the capacity of the lift truck and the capacity of most lift trucks is based on a 24" load centre or centre of the load.
There are standard sizes (width & thickness) to meet this capacity.
I would not want to put heavier capacity forks on a lift truck, it could be sending the wrong signal to the operator.
Dragging forks on the floor/ground will cause forks to wear out. Most/all lift truck dealers have fork wear calipers to check for fork wear. This should be done once per year maximum interval. Once a fork wears more than 10%, it (usually they) have to be replaced. 10% fork wear means the forks are now only rated @ 80% of their capacity and that's the cut off.
We're not talking about fork deflection here.