And when the dongle dies? Or someone thinks it's a USB key and walks off with it?
I have had both happen. No method is infallible.
The only licencing i really like it's Intouch's. Soft licence file. Yeah you could just copy it and run more copies than you have purchased, but hopefully all of us are professionals who don't steal
I find my most frequent failures these days are power supplies and hard disks. I use RAID arrays so a single disk failure isn't an issue and doesn't affect the licencing. Power supplies, no problem.