Depending on the source DNA seems to have a half life of 500-1500 years. This source calculates with slightly over 500 years. Permafrost samples may be more on the upper end of the scale but the message would be similar:

A study of DNA extracted from the leg bones of extinct moa birds in New Zealand found that the half-life of DNA is 521 years. So every 1,000 years, 75 per cent of the genetic information is lost. After 6.8 million years, every single base pair is gone.

https://www.sciencefocus.com/the-human-body/how-long-does-dna-last