I've owned a home (built in 1965) for 10 years, and my best advice would be to try and tackle one "major" project per year.
Beyond that, you should look into availing yourself of state programs to help save energy. For example, I live in Massachusetts, where there is the
www.masssave.com program that will give you a free energy audit and then a big discount on any work you get done based on what they identified.
In terms of specifics, do yourself a favor and spend the $$ to get an insurance company that won't %*@& you over when you need them. When it was discovered that a tiny toilet leak had - over time - led to a huge amount of problematic mold behind the walls (what other posters say about water is 100% true - it can lead to nightmare scenarios), my insurance company figured out ways to classify the damage so I wouldn't exceed policy limits.
And lastly, don't do things with your house to keep up with the joneses. It's really dated at this point, but read Millionaire Next Door, since a lot of its messages still ring true.