WM has been running for several days without being restarted.
While trying to build a 4k map, it was reporting over 1000 heightfields active and was running out of memory instantly.
I then created a new file by doing a save-as, and deleted everything except for an erosion node. Note that I did not restart WM. It now ran without complaining about the memory, but still had listed well over 1000 heightfields active. It also said well over a gig of memory was being used. After a bit, I cancelled this build, but the app froze up and I had to kill it.
Upon restart, opening the original file (before deleting everything), I hit build and - lo and behold - it worked. It maxed out at 86 heightfields active and somewhere around 400MB of ram.
I will now keep an eye on this to see if there is actually a leak, but I thought I would post this info.
Ben