What you may have heard about is included in the Austro Engine maintenance manual:
For E4 (marketing term "AE300") engines on the DA40NG (E4A), DA42NG (E4B), or DA42-VI (E4C) there is no recommendation for cylinder head replacement.
However for E4P-C engines (marketing term "AE330") on the DA62, the Recommended Maintenance chart of the Austro maintenance manual includes cylinder heads to be inspected every 300 hours and replaced every 900 hours. But because this chart is included in Chapter 5 and not the Chapter 4 Airworthiness Limitations section that must be approved by EASA or FAA, replacing a head is legally NOT REQUIRED -- it's only "recommended maintenance."
You may recall that when the DA62 was first certified, its AE330 engines had a TBO of only 1000 hours, in contrast to the then-1500 hour TBO of AE300 engines. Shortly thereafter -- based on positive experience with these engines out in the field -- Diamond/Austro extended the TBO to 1800 hours for both the AE300 and AE330.
Because the DA62's AE330 engine can run 6% more turbo boost pressure in the cylinders (180 hp instead of 170 hp for the AE300), and has a MCP (Maximum Continuous Power) that's 95% of 180 hp (vs. 92% MCP of 170 hp for the AE300), Austro chose to be conservative and recommended AE330 cylinder heads be replaced every 900 hours.
But this is just like specifying an engine TBO. In N-registered planes flying under Part 91, replacing a head, just like engine overhaul, is not required at a specific number of hours. If an owner wishes to continue operating the engine past TBO "on condition" (e.g., it's not making metal and compressions are still good), the aircraft can continue to be operated safely.
As more experience is gained with the growing fleet of DA62s, I wouldn't be surprised if Diamond/Austro eliminates the 900 hour AE330 head replacement recommendation so that it match AE300 engines (i.e., no replacement recommended).
I personally don't plan on replacing engine heads on my DA62 when they reach 900 hours.