I've rendered images for a 150 meters banner a few times and after calculating costs, render time etc I convinced the client that 45K width will do. If the banner will not be viewed from a distance of 1 meter, 150dpi is not needed at all.
If Max crashes you can render out tiles. You'd set the resolution to the final values, and then render tiles in 'crop' mode to save memory.
But with 64GB you may run out of memory when comping the image at the desired resolution - it's going to be ~21.1 GB for RGB with Alpha (~16GB without). Whatever it is that you need to do in PS, it's going to be *very* slow and saving alone will make for a nice coffee break.
FWIW, Max' UI will not allow you to use any number higher than 32K for output resolution, you can override this by using maxscript, however.
Also, PS used to have a 65K limit in the past, not sure if they changed it in more recent versions, so keep in mind this could be limiting the output resolution...