A different strategy for larger early withdrawals is in a post long ago where we talked about the three bucket approach. I'll likely never find it, so here is a brief summary:
Divide your retirement portfolio mentally into three buckets.
Bucket 1 holds the portfolio for your long term survival needs, AFTER social security befefits have been factored in. It lets you get by at the lowest standard of living that you would accept. It needs to be extra safe, for obvious reasons. If you figure that spending is ~$10,000, then you'll need $250,000 (at 4%) in your first bucket.
Bucket 2 holds the portfolio that gets you to the date when social security kicks in. Say you expect $15,000 in social security, starting in 7 years. Well, given the short time frame, you can withdraw at about 10% and still be safe for 7 years, so you only need $150,000 in the second bucket to get you to when the SS checks start flowing.
Bucket 3 generates your "play money" - for travel, for hobbies, and so forth, for all the things you want to do upon retirement that you could never find the time for before. You've already covered the necessary expenses out of buckets 1 and 2, so you can afford to take a higher risk with the withdrawals in bucket 3. Depending on how you see you expenditures occuring during retirement, you might not need to plan this bucket for 40 years -- maybe only 20 years, for example.
The beauty of this approach is that chances are awfully good that your safe withdrawals out of bucket 2 won't depete that portion of your nest egg -- that would only happen in a worst case situation. Depending on how risky you are with bucket 3, the same might apply there.
Dory36