It seems to depend a lot on what it means for someone to no longer be involved in the EA movement. The relevant alternative in my mind isn't donating nothing.
Speaking for myself I can certainly imagine not being involved in the EA movement in 2-3 years. It's a lot harder to imagine myself raiding a dedicated bank account I had set aside for donations. That doesn't mean it's not possible, but if use the population estimates of not being in the EA movement in 2-3 years of 25-30% (which seems reasonable) as my own risk, I'd estimate the risk of raiding a dedicated bank account for charitable donations as a fraction of that - maybe 5%. In that case it could be worth it. Maybe I'll think a little harder about that point if I decide to do it.
I 100% agree with the principal behind your post. The future, including your future identity, is so uncertain that for almost everyone the best time to donate and form altruistic habits is right now. I would only "bunch" if I could do so in a way that allows keeping those good habits.
It still seems like it could be worthwhile in the 2-3 year timeline if you were diligent about setting up good systems. I.e. you could set up a separate savings account that you put your yearly (monthly/weekly?) donation into and then donate every 2-3 years.
For me, at least, I think this would do a lot to decrease the cognitive load and temptation to spend. I don't do this currently but am thinking about it. If you can truly think of the money as already donated when in the separate account (maybe a wealth front cash account?) this would solve a lot of the problems. I do think I would end up donating significantly less when bunching if I didn't keep the money separate.
Good point about CS - I should have mentioned that in my post. A lot of economists are starting to dip into machine learning and do some heavy computational stuff where CS background is very useful. Also recommend everything else Howie said as well.
Another point for masters programs, especially for econ masters, is to see if they'll let you take PhD level courses in your second year. If you're very confident in your ability to take a PhD level course year 2 and you do well in it that would greatly increase your odds of getting into a top 6 program (particularly intro PhD microeconomics theory). Doing badly in a PhD level course decreases the odds, of course, so that's a risky path.
Quantitative masters are definitely a good path.
I believe the best options are:
1) Master's in statistics. If you don't have a quantitative degree from undergrad, getting into a competitive statistics program may be difficult, though. Most good programs expect at least a semester of linear algebra, multiple calculus courses, and some statistics. But, there are exceptions. The skill overlap between economists and statisticians is pretty large and admission committees love to see applicants with strong stats chops. If you cannot get into a statistics program due to lack of mathematics background I'm a little less confident in any other masters program recommendations.
2) Master's in economics in Europe from a good school. A masters from LSE or some other equally good school in Europe is a great signal and is probably as good an option as a statistics masters in the US . I believe the mathematics requirements are little less stringent here, but this may vary from program to program.
3) Any other quantitative masters program that teaches you linear algebra, calculus, and some statistics. This is if you can't get into a statistics or European econ program. I don't have particularly insight about good programs in this category, but look for programs with good research opportunities (especially if you can do research with an economic bent) so you can form relationships with professors and get a good recommendation letter.
An masters degree in economics in the US could fall into this category, but careful. My impression from talking to many PhD economists, including some that have been on admission committees for grad programs, is that an economics masters in the US is viewed as something someone gets because they couldn't get into a PhD program (and is thus low status). They're generally less rigorous than a statistics degree. There are exceptions, of course, and if you blow away faculty in your masters program with your talent and hard work you'd still likely get into a good PhD program. There are massive differences in quality across schools when in comes to their econ masters programs so research carefully and email current students if you take this route.
Possible better option than the above: get a research job and take math classes while working in your free time. Specifically, take linear algebra, calculus, real analysis (plus any prerequisites), and mathematical statistics. Differential equations is also helpful. Your grades in these math classes are extremely important to your admission probability for any economics program - probably the single most important part of your application.
Background: I worked as a research assistant for the Federal Reserve after undergrad and applied and was accepted to several mid-tier (roughly rank 15-40) PhD programs before eventually deciding I didn't want to do a PhD. I took a few math classes while working at the Fed (they paid for me to take them - a great deal).
Up-voted for interesting idea and for reminding me that Huemer is blogging.
I'd tread very carefully with something as physically and legally dangerous as this (or the black market non-profit), of course, and consult with lawyers before even considering it - maybe something related to this is the reason for the downvotes?
I agree it's a potentially valuable cause, but I think any less dangerous options that would move America towards allowing paid organ donation should obviously be preferred - off the top of my head I'm not sure what that would be, though.