If you are looking for the best fidget spinner around and are willing to spend some money then check out https://metalvorks.com/ I just purchased their Spinner v3.1 and it is exactly what it describes.
I have clocked this spinner coming in at 8+ minutes and could probably hit 9 minutes if it had a perfect spin.
This is not a spinner for kids (They will probably kill themselves with it) This is a heavy spinner. If you want to feel like you are getting your moneys worth then this is the spinner you should opt for.
There are few other high quality long spinning fidget spinners that I will be reviewing but so far this takes the cake. the carrying case is high quality and the 606 hybrid ceramic bearings really shine over any other spinner I have used.
I will make a video of this spinning to upload in the near future so stay tuned.