to create an account which valid for 7 days at fastssh.com you have to use a trick:
1. Open Fastssh website then continue to create SSH account page, for example, https://www.fastssh.com/page/ssh-account-creator/server/2/SSH-Server-USA-New-York-1/
2. Fill in username in the right field (Create account for 1 week)
3. After you have redirected to a new page which has long article, scroll down to find the button >> Continue Create Account then click the button
4. Next, please select Softether menu and create Softether account as usual, the difference is this time username in the SE menu will be filled itself and will automatically valid for 7 days.