When signing up for multiple cards on an ongoing basis, how do you handle the pile-up of all the annual fees?

I see some bloggers sign up for 6+ cards every few months. As they do not mention canceling their previous cards, it seems that they would rack up substantial annual fees for all those cards.

For instance, if they sign up for 10 cards in one year, each having an annual fee of $100 (give-or-take), that $1000 annual fee seems hard to justify. [Take it one step further; if that same person signs up for 10 cards, three years in a row, they now have a $3000 annual fee].

Are the sign-up points worth the on-going annual fees of having so many cards? Or, is there a strategy of cancellation when doing so many on-going sign-ups?

Thanks!