I think too much is made of the "limited" in "limited edition". I certainly don't believe you should destroy the negative. A print is the culmination of a number of factors: materials, time, skill, purpose. All of these can and do change. For most fine art prints the negative represents only a small part of the finished print, like the score of the music on a CD. A limited edition is the aggregate of a particular negative, materials, effort and presentation, limited by what the technology can produce and the artist (and market)will accept.
Technologies change. I'm about to embark on new editions of some old negatives because I have new ways of producing an image from them. Destroying the negative prevents the creation of new visions from irreplaceable moments in time. To create some integrity in my editions, they are numbered, limited editions, ie, first edition, second edition, etc. Each edition is made with a different perspective, yielding a different print, even though the negative is a constant. This isn't to say I flood the market with editions - most photos don't yield more than one edition...yet.
A good many negatives have historic value when properly archived. Burning makes little sense, as does destroying your work before you die. Your work is your legacy to your children in the literal and the figurative sense. It is presumptious of you to second guess the value of your work to future generations, however humble it may seem to you.