Six months is hardly a long time to be idle. I would just remove and reinsert the tubes (or better, clean the tube pins and the socket) to assure good contact and then power the amp up.
The concern with long-term storage has mostly to do with electrolytic caps that have begun to dry out. These can be brought back to life, but it is best done by slowly powering the caps up. But, this is a concern after years of storage.
Also, if your amp utilizes tube rectification, power naturally comes up a bit more slowly than with solid state rectification, so capacitors are given less of a sudden jolt.
The concern with long-term storage has mostly to do with electrolytic caps that have begun to dry out. These can be brought back to life, but it is best done by slowly powering the caps up. But, this is a concern after years of storage.
Also, if your amp utilizes tube rectification, power naturally comes up a bit more slowly than with solid state rectification, so capacitors are given less of a sudden jolt.