Let's put some flavor on that. A 1280x720 upload requires between 1.2 and 4 kbps going upstream. A 1920x1080 upload requires between 4 and 8 kbps. For a given resolution, it depends on the number of frames per second, color depth, etc.
So let's test at 1.2, 4, and 8 kbps:
1280x720 minimum 1.2 kbps ~= 0.5 Gigabytes per hour
1920x1080 minimum 4 kbps ~= 1.8 Gigabytes per hour
1920x1080 maximum 8 kbps ~= 3.6 Gigabytes per hour
Personally I think 720P is quite sufficient for most webcam work. If you have a lot of bandwidth available, then sure go for a 1080P feed why not.
Having said this, the place to invest is in lighting and sound quality. So few models get that right. Look at what Chloe Lewis does on her feeds. She nails the videography, the lighting, and the sound, and that is so much more important than going from 720P to 1080P. Learn three point lighting. Get lights that are sized correctly to your room. Play around with how those lights look on your body at different distances from the lighting. Get the sound arranged through a digital audio mixer to eliminate feedback loops and prioritize sounds the way you think viewers want to hear them. I think one model out of 20 does those things even at a passing level. That is where you can stand out, if you get things right.
I would rather watch a well-lit model with good digital sound control at 480P than a badly lit model at 1080P.