If you save it into another buffer or file it will not overwrite the previous one.
So if you follow the recommended approach 174 @alwynmathew mentioned, you can for example use the number of the current epoch in the filename.
Example:
model is the model to save
epoch is the counter counting the epochs
model_dir is the directory where you want to save your models in
For example you can call this for example every five or ten epochs.
torch.save(model.state_dict(), os.path.join(model_dir, 'epoch-{}.pt'.format(epoch)))