If you were lucky enough to see the full totality, then chances are you will save your glasses Forever. But if you saw just part of it, they may wander away. If you do cel nav, there is a use for these, so they are worth hanging onto.
The most accurate way to measure a sextant's index correction involves looking directly at the sun—which is not at all a part of normal cel nav. We normally look only to the horizon below it for regular sights, in which case the stock filters on the sextant do the job. To do the special "solar index correction," on the other hand, we look right at the sun with the sextant set to 0º 0', so we need exactly the type of filter used for the eclipse viewing. This type of filter foil is normally rather expensive. The price is lower when thousands of square yards are produced at one time, and many government agencies subsidize the production of them.
We discuss the technique and how to make the filters in both our books Celestial Navigation: A Complete Home Study Course and How to Use Plastic Sextants: with Applications to Metal Sextants and a Review of Sextant Piloting. It is the same method used by Lewis and Clark and other early land based explorers. The special filter we need for the sextant scope can be made from these glasses, more or less as explained in those books.
Work forms for the solar index correction with some brief level of instruction can be dowloaded as part of complimentary work forms package we have at the cel nav book support page.