How to use safety recaptcha? after some fail submit

Hi.

I'm using the invisible flow and is working nice. but I have a question since I have to pay for this service and I would like to know if should the captcha load as is it's or should limited after some submit happen and then show it.

let mi try to explain better:

Let the users introduce incorrectly user and password 3 times.
After the third failed attempt, the captcha must be also resolved.
After another 3 failed attemps, the user will be temporaly locked out at IP level (a few minutes).

So, my question is: will it be safer to show the captcha from the beginning? Some time ago, a lot of websites used to show it after n failed attemps, but now they prefer to make sure the user is not a robot every time he wants to be authenticated. Is there any reason to really do that?