Per the Sw site RR FAQs:
Do the points I earn expire?
Points do not have an expiration date and will continue to remain active and valid as long as you have at least one qualifying earning activity every 24 months.
Can I book travel with points for other Passengers (not me)?
Yes. The Rapid Rewards Member who owns the account from which the points will be used will need to make the reservation for the person traveling. Simply get the destination, travel dates, and flight times from the person who will be using your points and log in to your account at southwest.com (password required) to book the reward travel. Reward travel is subject to the government-imposed September 11th Security Fee of up to $10 per roundtrip, which must be paid with a credit card.
The offer on the SW site is for 50,000 points $99 annual fee and 6,000 Anniversary bonus points every year.
My husband received an offer in the mail for 50,000 points, $69 annual fee but only 3000 Anniversary bonus points every year.