Hello Chao,
It depends on which course you are talking about.
For example, the Top 10 USDJPY/EURUSD/GBPUSD trading courses, i just update the EAs every month or two with new parameters according to the recent market conditions.
But for the other trading courses, as the Automated Forex trading + 99 Expert Advisors, Forex strategy course – Portfolio trading with 12 Expert Advisors, and most of the crypto courses, I upload new EAs every month.
It is really a personal choice if you want to delete the old ones, and put the new. Or you can keep adding new Demo account and select the Top EAs from more than 99 EAs..up to you.
Kind regards,
Petko A