I've had a VFD on my mill for a year or two, with no problem. This is a home shop, with home shop level use. As a practical matter, I doubt you'll run into trouble. If your usage is anything like mine, you spend far more time setting up, changing tools, and figuring out what you're doing that you do actually milling anything. What's the actual time you're running? Maybe 10%? The motor doesn't have time to heat up much.
Try to make a living, not a killing. -- Utah Phillips
Don't believe everything you know. -- Bumper sticker
Everybody is ignorant, only on different subjects. -- Will Rogers
Law of Logical Argument - Anything is possible if you don't know what you are talking about.