configディレクトリのjwt.phpのファイルで設定できる。

jwt.php

    /*
    |--------------------------------------------------------------------------
    | JWT time to live
    |--------------------------------------------------------------------------
    |
    | Specify the length of time (in minutes) that the token will be valid for.
    | Defaults to 1 hour.
    |
    | You can also set this to null, to yield a never expiring token.
    | Some people may want this behaviour for e.g. a mobile app.
    | This is not particularly recommended, so make sure you have appropriate
    | systems in place to revoke the token if necessary.
    | Notice: If you set this to null you should remove 'exp' element from 'required_claims' list.
    |
    */

    'ttl' => env('JWT_TTL', 60),

デフォルトで60(1時間)に設定されている。
ここを変更することで設定可能。