matador,
I usually start each cycle with about 35-40% of my dedicated option capital in play. Depending on the market action, I may increase a bit as time goes along. I prefer to always keep some powder dry. I also won't hesitate to use up some of my monthly credits to adjust away and increase my breathing space and rebalance my portfolio deltas somewhat. In fact, I keep close track of the net credit for each month in a spreadsheet, and don't consider that extra cash as mine until all the IC's for that month are closed. For me, it is a defence fund to protect my capital, and if I wind up using it all, I'll close the IC for that month, take a short breather, and then set up for the following month. That way, typically my losses will be minimal when they occur.
Like many other experienced players, I much prefer to avoid expiry and I personally like to set up my new IC during the last week of the old month. I know that Mark W. likes to buy back the old IC for 15 cents to 25 cents per side whenever possible. I am quite happy to do that, as well. After all, the next month IC will be worth more with a week extra to go anyway. Some, usually about 1/3 of the last few cents, can be recouped in the new month IC's additional value, and the risks are significantly less.
Adjusting an IC with 5 weeks to go is a lot easier than one with 2 or less weeks to go. In fact, early in the life of the IC, if the market movement is reasonably orderly, and the vol does not substantially increase, many times the adjustments can be done without incurring any additional costs. Later in the life of the IC, this becomes more and more unlikely unless market conditions have been quite favorable.