You could for sure give it a static inside whatever prefix you get. But if they happen to hand you a different prefix all your scopes can change on you.
Why they don't just assign customer prefix XYZ, /48 should be what they give you and be done with it..
If you want static and your ISP will not give you one - just head over to hurricane electric and grab the free /48 they will give you. Now you have all the statics you want ever.. And what is nice is even if you change ISP you can just keep that /48.. Even if your isp doesn't support ipv6 you still have that /48, etc..
I have had the same prefix since 2013.. And even can setup PTR on any of the IPs I want in that /48 and recently moved to isp that doesn't have any IPv6 and means nothing to me.. Since it took all of 2 seconds to setup my tunnel again with all my boxes able to have the same exact ipv6 address they had with the previous isp.
Really the only draw back to tunnel is a few extra ms latency vs native connectivity - depending on where the nearest pop and where HE peers with your isp, etc. But they have pops all over the world.
https://www.tunnelbroker.net/status.php