Im not sure if we are talking cash games or sngs here..
But, from my point of view, taking a shot at higher limit just to push your comfort zone a bit, to see how you will do, to see what are the differences, is totally ok, given that you are well rolled for you current limit and you are only shooting one limit higher.
The worst thing that can happen is you loose couple of buyins. But you can also win couple of them.
So if its not really aggro brm shot, id say go for it.
I think there is nothing wrong about being conservative with brm, because lot of ppl dont have strong enough mindset to deal with moving up and down limits all the time. But taking one shot at games you think you have edge on is fine, you need to push your comfort zone a bit, so next time you play ur regular limit again it might even seem easier and more confident