The scan duration depends
- on the settings
- which drive(s) are scanned
- how many files are scanned and whether there are rather many small ones like in the Windows folder or big ones
- to some degree on the general computer performance (CPU if you have a really old model or your computer is working poorly in general)
- to some degree on the on the signature database, which is constantly increasing
However, even with maxed settings (max effectiveness, scan whole file, unpack archives) and over 3TB of scanned data (and even without a SSD as a system drive) I've never come past one and a half hour of scanning, except for when I've let it scan with the "ask me what to do when a thread is found"- option and it had triggered some false positives while I've been away from my computer.
The first thing I'd advice the OP to do would be to check the
SMART values and general health of the scanned drive with
CrystalDiskInfo.
If you want real performance with scanning, get a decent solide-state drive with enough capacity for Windows and all your programs and a normal hard disk drive or an hybrid drive with 7200 rounds per second for storaging purposes although it would be faster, if everything was scanned on a/some SSD(s).