As long as TDA will hold the position and not charge for it, it can be held until the offset of gains is most effective (ie - in a "good" year or maybe when the IRS is owed a check when taxes are filed). They won't close it partially, it'll be all or nothing, just make sure the loss is covered with gains.
Given the state of the exchanges (ie - tanking with the pandemic), there may be better years in the future to close it out.
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