Upgrade a new ticket is what I typically do. I can usually get a bit of a savings from a discount ticket seller (usually
Undercover Tourist) that I upgrade which helps with the math when figuring out whether to take the discounted AP renewal rate or to buy a new pass that's good for a whole year. If you're not going between November and May, that's a whole six months that you're paying for an AP you're not using!

But other people like just renewing at the same time every year and knowing they always have a pass.
My logic breaks down like this: we tend not to travel much in the hottest part of the summer so my passes have gone from May '14-May '15, October '15-October '16, December '16-January '18 (13 month promo) and then April 18 -April '19. If I had just done renewals, those four annual pass costs would have only carried me through to May 2018, but instead I have a pass good through April 2019, almost a whole extra year. Even accounting for the value of the four renewal discounts (this year it's about $136), the total value of the renewal discounts added together isn't enough to pay for 11/12ths of an annual pass, so I've come out better by NOT renewing. I have no idea if I explained that well, but I just hate the idea of paying for an annual pass during the 25% of the year I know I'm not going to be using it.