I like to leave them in for around 2 weeks, about twice as long as many recipes call for but I also like a stronger vanilla flavor than many beers with vanilla offer. In many pumpkin beers I feel it's used to smooth out the spices and provide a background "sweet" flavor.
6 weeks of oak for a 5% beer seems like a long time to me as well, but I have only done a couple of beers with oak cubes, never used spirals. But, if you're confident in your timing there I would say you have 3 options:
1. Age it on the oak for 6 weeks and transfer to a secondary with the vanilla beans, unless you can easily pull the spirals out, in that case pull the spirals out and put the beans in.
2. Put the beans in the primary and taste after a week or so and let continue aging until it has the vanilla presence that you want, then transfer to secondary with the oak spirals.
3. Put the oak spirals in, allow it to age 4-5 weeks, then put the vanilla beans in, and taste after a week and continue aging with the beans and oak until your happy with how it tastes.