What is interesting is that the first launch of the Falcon Heavy is not really representative of the Falcon Heavy.
The side boosters were previously flown Block 3 Falcon 9 boosters. (Thaicomm-8 and CRS-9 mission boosters).
The core booster was a new design based on the Block 3 Falcon 9.
Every other Falcon Heavy will be based on the Block 5 design. While it is still a Falcon 9, still using the Merlin 1D engines, it is a modified design, in apparently some significant ways. They will be getting 10% more thrust out of the engine. Reusability is expected to be much more simple.
Thus the next Falcon Heavy to fly will be similar, but not quite the same.
However this will be mitigated by the Block 5 Falcon 9 single stick likely flying multiple times before the next Falcon Heavy.
This is quite interesting from a certification perspective and the fact there will be no test of the all up Block 5 Falcon Heavy.