Yes, there's a VERY seasonal nature to these offers. Of course they're intended for the spendy knuckleheads, so non-MMM'ers should steer clear.
BUT... sometimes you can get really good offers for points if you're doing MS (managed spend) that you won't see any other time of the year. But the best way to deal with them is to decide BEFORE the holidays which offers you'd like to see - which cards / points-systems you want to add to - and watch for only those offers. Then when they come in, do a good internet search (at sites like frequentmiler.boardingarea.org and travelmiles101.com) to see opinions from long-time MS'ers regarding that offer as compared to previous years offers, other cards etc.
Happy Holidays!