Authentication tokens keep expiring

I've got some python code that uploads files to my dropbox folder, but I must be doing something wrong, because my authentication tokens keep expiring, despite multiple claims that these tokens should be long-lived.

I'm not using the test-api, but rather I did the following:

dbx_oauth = dropbox.oauth.DropboxOAuth2FlowNoRedirect(DROPBOX_APP_KEY, DROPBOX_APP_SECRET)
url_for_oauth = dbx_oauth.start()
print(url_for_oauth)
# Follow the link, get a short code, copy it, and paste into the finish method:
oauth_result = dbx_oauth.finish('SomeCodeOrOtherBlahBlahBlah')
print(oauth_result.access_token)
# I now have a TOKEN that I use for the rest of the day...

But as mentioned, this token expires and it's driving me nuts because it's messing up my work-flow.

What am I doing wrong?

Also, being the "owner" of my dropbox account, couldn't I bypass this whole token thing by using my app-key and and app-secret directly somehow??

 

Thanks!