My calculation on this topic.

A successful mint matures for about 10 houres. With one minute medium block interval it's 600 blocks in total. After 600 blocks they can mint again.

We have a total of about 77 Million coins. If they would mint alltogether in an even way, the absolute maximum fragment size would be 77.000.000 blk / 600 = 128.000 blk.

Not all are minting, of course, and some coins get lost, so the optimal split size should be much lower than 128k. To be cautious, one could double the size from time to time until it fits. So the devs could double the split size from 1k blk to 2k blk on a next release.

Regarding this and the attack, not only the processor load is affected, but the resident memory load too.