Always better to be safe than sorry (complacency is the greatest enemy of any system).
Re S&D, Adaware and CCleaner they are useful tools to run as part of a security/cleanup routine - for some this is a daily task. For others once a week and some once a month - the choice is yours and should be one that fits in with your way of working.
However along with a good backup regime a regular security sweep does no harm and is considered, by many, a good working practice.