thanks for trying to help me. i'll have to call it a bust for the time being.
since you mention a bug in the nvidia driver, i'm leaning more towards that as the culprit. another voxel game i play, 7 days to die, similarly will crash after a period of time. i tried that game under windows last night and both 7 days and rising world on windows 10 ran smooth as butter. the only commonality between them [besides voxel stuff] would have to be the driver.
if i remember right, when i skimmed the nvidia experience panel i think the version number was higher than the linux one, but i just assumed it's because windows is the main focus of support. somewhere i have a ppa for nvidia drivers bookmarked, i'll have to try adding that and see if they have a newer driver prepackaged.
as far as the mint repos are concerned my installed driver is:
4.6.0 NVIDIA 435.21
oh well. situations like this are precisely why i still keep windows around. thanks again.