I am not convinced that martingale and grid system are good.
With a large enough account balance, and the smallest possible trade units or lot sizes, martingale and grid systems can be extremely profitable.
However martingale and grid systems are not the same thing. Grid systems do not always use Martingale.
Martingale is generally used to calculate the size increment level of the next trade that you are going to open.
Martingale doesn't have a specific entry and exit point.
Your entry and exit points would be determined by your trading strategy.
Martingale determines the size of the trade.
There is no way of knowing when they will fail.
In general it should be noted that all trading strategies will incur losses at some point.
It is fine if you get a good patch and make 800% before they fail but equally you could have only been using it for a month before it fail and wipe out your account. Martingale is best avoided.
Again, the same could be said about all trading strategies and the discipline level of the trader.
Emotions in trading will typically be a greater threat to the investment capital than a martingale system would.
Martingale is a calculation method used to determine the lot size of the trade.
Your entry and exit points are determined by your strategy.
If a trader is using a high risk strategy with a small account balance, then there is a far greater risk of blowing the account.
If a trader is using a low risk strategy, trades very carefully using very small trade sizes, and has a large account balance, then there is less of a risk of blowing the account.
There are many things that have to be considered.
If it looks too good to be true, it's probably a scam! Let the buyer beware.