is MT5's demo accout 30 days limit?

how can I let the demo account for never expired?
Documentation on MQL5: Standard Constants, Enumerations and Structures / Environment State / Account Properties
  • www.mql5.com
Standard Constants, Enumerations and Structures / Environment State / Account Properties - Documentation on MQL5
If you mean MetaQuotes-Demo server you should connect using your account not less then once in 120 days.
do you mean is demo account only for 4 month only?
Documentation on MQL5: Standard Constants, Enumerations and Structures / Environment State / Account Properties
  • www.mql5.com
Standard Constants, Enumerations and Structures / Environment State / Account Properties - Documentation on MQL5
The period is prolonged each time you connect with the account.
codeidea:
do you mean is demo account only for 4 month only?

It depends on server settings. Demo account on MetaQuotes-Demo will be deleted after 4 month of inactivity.