1) From everything we've read, Hondas and Toyotas make the most reliable minivans. This, of course, also means they're the most expensive used ones. Have others found the premium paid to be worth it in the long-run? We do plan to keep the thing until it dies.
I'm the type that usually buys quality things that I like & keep them long term. This applies to things such as clothing, jewelry, household furniture, wives, and of course cars. So I'd say get the best you can afford & keep it until the wheels come off.
2) Because we want to keep it for a long time, we don't want something that will die in just a few years. However, we also don't want throw money into a new car. Is there an ideal age we should be looking for? What about mileage? Corollas/Civics can go 200k+ miles easy, what about their Minivan counterparts?
I'd image a Honda/Toyota van would go the same mileage. I'd shoot for one a few years old & 50k miles as a rule of thumb. Just shop around.
3) I know prices vary a bit by region, but can anyone share how much they paid for a similar used vehicle?
Never owned a mini van.