eeswun,
Timing the market is for experienced investors as Tom informed you. I, for one, am not experienced enough. The best I can do is have a few allocations. One for a good market, one for a normal market, and one for a bad market. In your case, maybe use the L2040 for a good market, the L2030 for a normal market, and the L2020 for a bad market. By the way, each of those funds has a percentage of their holdings in the 'G Fund' along with the other funds (F/C/S/I).
Here are your numbers on your market timing experience.
Starting Value on July 15: $40,000
Ending Value on October 14 in the 'G Fund': $40,212
Ending Value on October 14 if in the 'L2030 Fund': $37,747
Difference: $2,465
So, your experience in market timing has saved you about 6.5%. And, September and October are notorious months.
Here are the negatives:
You have about 23 years to go till retirement (a very convenient number because we can use the fund inception date).
Investing $40K in the C Fund for the past 23 years:
- Average Return: 9.55%
- Your $40K becomes $325,945
- You annual income of $33,880 - $13,528 inflation adjusted.
Investing $40K in the G Fund for the past 23 years:
- Average Return: 5.93%
- Your $40K becomes $150,486
- You annual income of $12,315 - $4,764 inflation adjusted.
And, the 'G Fund' was making 9% in 1988 and 1989. Will we see that again? Even with the big numbers early the 'G Fund' doesn't cover your rent - and that 'Rent Is Too High'!!! You will be forced to the off label Alpo. And, good God, think of what recent 'G Fund' returns (3%) will do to your retirement.
Why worry about 20 months when you are investing for more than 20 years? I would glue it in the 2030 till I gained more knowledge. At that point, personally, I would shade my holdings a little one way or a little the other way. That way you will always be able to take part in market gains that come along 'unexpectedly' (like our current unemployment numbers

). For you, 'time in the market is far more important than timing the market'.