Google Drive AccessTokenLifeTime

I'm wondering if you can explain the Google Drive AccessTokenLifeTime function, as in what exactly the integer it returns represents.

What we are encountering is an occasional error when uploading. Once the error occurred when simply uploading a file when the app had been idle for a couple of hours, and once it occurred when I was doing a giant upload of a folder that contained 3600 files. It failed about 2/3's of the way through, which was somewhere between 60 and 70 minutes.

The debugger showed the JSON in the exception. I didn't capture the text, but I did get a screenshot of the error, but I can't figure out how to upload it here.

The json error contained:
domain: global
reason: authError
message: Invalid Credentials
locationType: header
location: Authorization
code: 401

After this error, trying to refresh (clear and get drive info) gave the "No drive info returned" message, but exiting and restarting allowed the app to get into Google Drive without a re-authorization prompt, so I don't think it's a token issue.

I'm wondering if the upload needs to check for the error and try to refresh the tokens?

I was able to reproduce the problem just now after letting it sit idle for 60 minutes.
I'll add a refresh tokens call before the upload and see if that fixes it, if it does then I can figure out exactly how often that should happen.

This is the json:
Project Places.exe raised exception class Exception with message 'Upload Error: {
 "error": {
  "errors": [
    "domain": "global",
    "reason": "authError",
    "message": "Invalid Credentials",
    "locationType": "header",
    "location": "Authorization"
  "code": 401,
  "message": "Invalid Credentials"

Trapping the error and doing a RefreshAccess and trying the upload again worked.

The Google token lifetime is 3600sec. A RefreshTokens call is indeed needed.
With AdvGDrive.AccessTokenLifeTime: integer, you can retrieve the remaining access token time (in seconds)