Not to state the obvious, but you could also just buy more tickets...
I mean the other ideas are more cost-efficient though, of course. However, sometimes an annual pass doesn't make sense at the time - you may not know when you're going back to Disney or you're planning on getting a dining plan, so you need at least 1 ticket anyway. For me, the annual pass was just too complicated/not quite right for my needs at the time I wanted to book my trip. I may very well get one in the future. Also, alot of times, at the time of booking, I only have the $200 needed to book and not the amount needed for an Annual Pass. For whatever reason, even if it makes sense to get one, it's never worked out for me to get one at the time.
My trips tend to be 10 day+ stays, so I always have to decide what I'm going to do about tickets. In other years, I did Downtown Disney and/or Universal as well or elected not to visit the parks on flying days. However, I have often still needed more tickets. So, I have just bought them. When I'm planning my vacation, that is when I decide how many days I want in the parks and if the 10 day ticket doesn't accommodate me, then I will just buy more - I look at it as another vacation expense.