Octane 3.06 has Adaptive Sampling which will be a solution to your problem. They're currently working on implementing the changes into the 3DS max plugin, but there is no solidified release date. It may be a couple of weeks.
GTX 1080Ti 11GB (3x), Water-cooled Intel i7-5820K 6-core @ 3.3GHz Windows 10 Pro 64-bit, 32GB RAM