I recently added MBAM (free version) to my defense "arsenal", so now include that and SAS for my weekly on-demand scans. Since both products update with full-database replacement rather than incrementally, I quickly decided there was no point updating other than just before a scan.
One other thing I'd like to see changed for both products, besides incremental updates (if possible). Neither one apparently cleans up after itself after updating, so there's 3 or 4 megs of temp files left behind each time that need removed with Disk Cleanup. Not a big deal, it just seems a little sloppy to me for such otherwise high-quality apps.