How often do you use a at home doppler?

I used it for 10 mins or so yesterday and couldn't hear it.

I used it for about as long today and finally got it.

Totally forgot my appointment tomorrow they will listen too.

I dont want to use it too much!

I'm going to put it away for awhile so I don't make a mistake like that again.

Have you used yours more often and everything been just fine?