Generally, service providers will contact you shortly after you cancel service (if not earlier) trying to get you to come back. If you contact them, though, it may not work as well. I don't remember where DirecTV fits in the spectrum, but generally service providers have a specific period of time before they will consider you a new customer, vis a vis taking advantage of their deeply-discounted new customer promotions - some as long as 18 months, but others as little as 4 or 6 months. I'll try to track down the specifics for DirecTV if I have a chance.
EDITED: Official policy is evidently one year, or a change of address. Note that you would not really be a new customer; so if you had encumbrances on your old account, they would be carried over to your new account.