Hi @chongjasmine, There are many good answers from others. But just put some summary.
I am using EA heavily. MT4 and MT5 are the same, you need to keep it on to let EA works. If you can’t maintain your personal computer to up 24 hours x 5 days, it’s better to use VPS.
You have to run the MT4/5 on the VPS. This is the best scenario for automated system traders.
Once you have set the EA, usually the configuration will be the same every time your start MT4/5. Unless your machine shutdown improperly. It may crash / ruin the configuration file, so the EA will be reset to default value.