Some of our expertise to try and claim via EU261, you mean. A ruling that is going to cost our industry unneeded costs in an already stretched industry. Believe it or not, airlines don't delay aircraft intentionally!
There could be many reasons why your aircraft was delayed for that period of time. Not all are the airline's responsibility. If downroute, a catering truck crashes into an engine and damages the engine beyond limits, that could cripple the aircraft indefinitely. Should the catering company or the airline pay up?
I apologise for sounding like a broken record, but airframe S/Ns make absolutely no difference to delay or no delay. A common perception amongst the great unwashed is that, the older the airframe, the more susceptable the aircraft is to unscheduled maintenance. Simply not the case. A320/1 MSN1 or MSN5000 could be as airworthy as each other, if the airline looks after the airframe and stringently follows procedures as set down by its own AMP, EASA and Airbus/Boeing. The oldest A300 aircraft for example still in revenue service is 36.3 years old (source: Airfleets), albeit converted to a freighter.
Airframes will be checked on a regular basis. Heavy maintenance on 5Y, 6Y, 10Y, 12Y, 15Y, 20Y, 25Y as well as a 1C check every 15 months approximately. Not many components will be the same at return/retirement than they are at delivery. Lifed components are replaced on a regular basis.
There are places you can find out which aircraft flew a particular route on a particular day, but its not me who's going to tell you!