The shop(s) airside at Munich are dreadful, with very limited choice and relatively high prices. Unless they have a very special offer, most whisky can be bought cheaper on the internet or even in many cases, on the high street.
When I travel, it's usually back to the UK and via Stansted, so a good long visit to WoW and a chat with the staff is usually a necessity.
As Munich is then my final destination directly from Stansted, I just buy and carry on board.
Ohhhh, did I mention I'll be back there for just a couple of das next week?