I've only played it once so I can't really comment on longevity. Your concerns are valid. We found that handling all the decks was a bit of a chore and the game does eat up a lot of table space. It also really should have included a battle board because you're expected to organize and play your cards in specific locations when a battle does occur and without a mat or board of some sort, it can lead to ambiguities. They have a battle board illustrated in the rulebook so it's a shame that they didn't include one in the game. Easy enough to make one yourself and print it out though.
My opponent and I both felt it was physically unwieldy but we also felt that the core mechanic of creating your own TOE with hidden units in each corps was a neat idea and we'd like to play it again at least once more to get a better handle on it.
Combat is brutally unforgiving, especially for the attacker and we both lost a tonne of units early on before we realized just how deadly combat is in the game. (I lost the entire French 1re Armee in a failed landing along the Cote d'Azure in August '44. The Germans lost the 1st Army and most of the 5th Panzer army attacking the Normandy beaches in July '44.