Muffs are an excellent addition in winter - either keep your hands warm enough directly or make heated grips/gloves much more effective. However, they aren't so easy to fit on the ADV as it has handguards. You can take them off, but such mechanical things are beyond me. I've been using overgloves this winter (in combo with normal winter gloves or heated gloves) and have found them very effective.

It's quite easy to take off the hand guard. Just two bolts hold them

I agree with MrGrumpy.
I've had muffs on nearly all my scooters. They are less easy to fit on my Forza 350 than on X9s and Silverwings but the Givi Universal ones do the job.
I had Heated Grips on my X9500 but found they didn't cope with wind-chill, the biggest factor in making hands cold. since they heat the bit which is shielded anyway.
I left the muffs in place throughout the year, wearing single-layer gloves in the Summer. My hands didn't get hot even in the warmest weather.
Each to his own, of course.