Anywhere 1.5a
Dopus 12.33
I have read in the Dopus help that if you have installed anywhere the calculation is instantaneous, but every time I open my local disks it does the calculation again.
Is there any configuration so that this does not happen and I can use it from anywhere?
Do you mean Everything? Opus v13 has native support for it.
In v12 you can get it with his add-in
Yes, Everything 
.
I understand that being native I don't have to configure anything?
I have a disk of several Terabytes and every time I close and reopen dopus it starts calculating the size of the folders.
Why does it keep calculating the size of the folders?
I have tried deactivating the option to do it manually, but it still calculates them anyway.
Yes, if you run Opus v13 and Everything 1.4. There are reports that Everything 1.5 already works as well.
If you run Opus v12 you'll need the add-in I mentioned. It will work with any version of Everything.
How v13 displays folder sizes can be configured in Preferences / Folders / Folder Sizes.
By reinstalling dopus 12 I have managed to get the error of turning off the folder size to work fine, perhaps some script or configuration was blocking it.
I didn't know that Dopus 13 was already available. I installed it to test and the everything 1.5a folder calculation doesn't work well, it keeps calculating the size. I'll try version 1.4
I have seen that the beta only lasts 18 days, is it possible to buy the update or get more days?
Currently neither, but the release is around the corner, and if there are delays the beta certificate will be extended.
Thanks