Thank you so much for the feedback.
Auto selling the stamps is such a smart move, I added a way to batch sale (1, 5, 10, 50, 100) at a time but auto selling is a much better solution. I guess it was one of those initial design decision I made, got used to and never thought about how annoying it is.
Again thank you and if i'll ever get to revision the game this would probably be my first fix.