Of course you can do too much, but there's a difference between a grand tour and a one day classic. It's very common to keep on training before a GT, because you have to get going rather than be completely fresh and focussed for that one day. In the last five days he will probably catch the last percentages of form and supercompensation, though.
I think that Majka, unless he really went down the drain or drank to much vodka in the last weeks, will be fine. The Giro gave him a very wide base and he can pick his days/moments to help AC. He can take it easy on the flat days, lose huge amounts of time, freewheel to the finish afther he's done his job and has no pressure. He just needs to believe in it and willing to this job.
I think that Majka, unless he really went down the drain or drank to much vodka in the last weeks, will be fine. The Giro gave him a very wide base and he can pick his days/moments to help AC. He can take it easy on the flat days, lose huge amounts of time, freewheel to the finish afther he's done his job and has no pressure. He just needs to believe in it and willing to this job.