Larry:
First, I don't think that a poorly degassed wine will blow corks. What blows corks is when fermentation continues in the bottle, and the generated CO2 builds up pressure.
Second, if you are concerned about CO2 in your wine, taste a bit. If you can taste/feel the CO2, you need to keep degassing. Another way is the 'poof' test. Draw a sample into a small bottle. Cover with your thumb and shake. If it goes poof (like a bottle of beer), then keep degassing.
Steve