I have 12 Radeon Pro Duo, 32 GB. Awesome cards and perfect for rendering. They also mine 50mhs per GPU. But nowadays it is not so profitable.
any idea what can I do with them? How to use them better? How to have more profit?
I mean other activities like rendering or whatever
Do you have any actual use for them yourself, other than mining? Installing them into workstations/servers, doing some calculations/rendering/etc? Or did you just buy them for mining purposes only? If it's the latter, then I'd consider selling them. They're currently $849 new, and sell for $600-650 used on ebay, still decent prices and they're very likely to start getting even cheaper soon.
Usually many people buy GPUs as gifts during that time.
True, but we're likely to have loads of used gpu supply this Christmas, so it probably won't matter much in his case.