Dan,
You are concerned about the fATPL becoming 'stale'.
There are two types of 'stale'. First, there's the legal type. Your written exam credits will only be valid for 7 years after the date of your last IR renewal. (At least, that's the way it works for modular, I assume integrated is the same but I don't know that for sure.) In other words, every 6 years or so, you must renew your IR, at the very least, or else you'll have to do the exams again. Other licenses and ratings also have finite shelf-lives if they are not renewed or revalidated, but these can usually be fixed fairly easilly.
Then there's the issue of you staying current. I assume that you would earn enough in your accountancy career to be able to spend some money on flying, in which case this won't be a problem.
And finally, there's the issue of building enough hours to make yourself more attractive to the airlines. Let's say you finish your course with 200 hours and find you're not employable, then go back to work for a year. A year later, you've managed to pay the mortgage, and even put another 50 hours in your logbook. But you will be no more employable with 250 hours than with 200. To make a difference, you will need more hours than you can reasonably manage to build part-time. So your only option would be to keep your fingers crossed and hope to get a shot at one of those few and far between (but not non-existant) jobs where 250 hours is enough to get you a look-in.
Good luck,
FFF
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