Issue token & cookie only valid for an hour or two?

[tectonic-pg]

I followed these instructions to get an issue token and cookie. They appear to work fine and give my app access to my Nest account. However, it seems the token/cookie then expires after an hour or two. Is there any way to make them last longer?

if (!isset($result->access_token)) {
    throw new UnexpectedValueException("Response to login request doesn't contain required access token. Response: " . json_encode($result));
}

// Response: {"error":"USER_LOGGED_OUT","detail":"No active session found."}

At the same time that I get these errors in my app, I am still logged in, on their website (on Chrome).