the first time I tried SAP, I uninstalled it in disgust, for the very same reasons that were bothering you.
then they came out with a new version and I decided to try it again.
By the way, every time you shut down or log off, it will do another full scan when you come back, although it is much much shorter than the initial one.
Nonetheless, it also gets stuck sometimes!
But not to worry, it doesn't suck your computer resources like the initial scan. You probably won't even notice it.