The papers are awash with Prince Harry and his engagement. While they have yet to set a date when they do no doubt they will both begin a fitness drive of some sorts. While I doubt I will be at the palace dishing out training sessions I have worked with many engaged people over the years.
Wedding focused training is a double edged sword, on the one hand you get a fairly well motivated person who will get great results but this lulls you into a false sense of security in evaluating how much they have really changed deep down. My goal when working with someone is to get results ASiAP- As Soon(ish) As Possible, but in a way that they can never go back to where they were before. Believe it or not, being really motivated can actually be a block to this latter goal.
Most wedding people want to be in shape NOW and use willpower and good motivation to progress forwards. If not careful this can come at the expense of changing longer term natural behaviour patterns. Most of your long term success is determined by how you act when low on motivation and willpower. Hence the results from wedding fitness plans can be worse in the long term than the average person without such a looming goal.
If done correctly though you can of course reap all the benefits at the same time. You can get results ASAP and change your behaviour for the long term.