How binding are lease renewal notices?

Seems most rental companies send these out, expecting them signed and returned within a short deadline so they can begin pre-leasing your place if you choose not to renew.

How binding are they? If I check "yes, I would like to renew" but change my mind within the months between now and actually signing a new lease, can they hold me to the renewal notice? It isn't a lease, just a piece of paper saying that you will sign a lease when the time comes.

Had one company make me sign it nine months in advance. A lot can change in nine months. Just curious what other renters thought of these and what experiences you've had.