Suede boots are easily damaged with continuous wear, particularly in inclement weather. Protecting them before wearing them out is the best way to ensure a longer life for your boots.
Scotchgard
Scotchgard is not recommended for use on suede boots or shoes. Essentially, Scotchgard is a cleaning agent intended for specific items including carpet, hardwood floors, fabric and auto upholstery and eyewear.
Alternatives
Alternatives to Scotchgard that are specifically made for suede shoes and boots include Kiwi Suede Protector, a can that costs $8.99 (Amazon.com) and makes your boots waterproof and stain repellent. There is also a Nubuck and Suede Spray On by Nikwax that costs $8 a can, as of November 2010. Other protector sprays are also available; ask your local shoe shop or leather and suede store for recommendations.
Suede Protection Tips
Brush the suede before applying the protector, ensuring that the boots are clean and stain-free. Place the boots on old newspaper and spray in a well-ventilated area. Make sure the boots have dried before you wear them. Keep in mind that some spray protectors will need re-application when exposed to water, or periodically to provide continued protection.