I think they actually changed and the Military Salute tickets now renew January. The MS tickets expire very close to the end of the calendar year because they are blacked out for Christmas. These are the most heavily discounted tickets, and only come as 4 or 5 day options, and you can add hopper/water parks or not. You do get a very very small discount on regular tickets (and pay no tax on them if you buy on base or at Shades) but even with that discount, it may be cheaper to get a 4 day MS ticket than a 2 days regular ticket with the small military discount. The nice thing about MS tickets is that the 4 or 5 days can be used anytime throughout the year, so you can go two days now and 2 days in November on a 4 day ticket. If you add the Water Park feature, you get 4 park days AND 4 water park days, making it essentially an 8 day ticket for a very low price.
The military member can buy up to 6 MS tickets per YEAR for WDW and another 6 per YEAR for DLR (unless the immediate family is greater than 6, such as Mom, Dad and 5 kids, then you can buy 7).
This site should have the best information:
http://www.militarydisneytips.com/