I used modo from 601 to 801. I stayed on 801 for a few years because upgrading to future releases meant being tied to either subscriptions or maintenance commitments. It's not an appealing option if I decide the latest release wasn't worth upgrading.

If there's an upgrade path with huge promotion from modo 801 to 17 I would consider it for old times sake.
I now use blender but I miss modo's modelling workflow.