I am in TSP as well. For the information of others, it is the government's equivalent of a 401k, where you put in money pre-tax, the governemt matches to some extent, and you have five low-cost index funds to invest in, as well as some lifecycle funds.
The problem was that people were actively trading their TSP funds. I know of many people that did just that. Doing so effects the costs, etc. of the funds, and the key is to keep the funds costs low, as right now the expenses are as low as any other index funds out there (our funds are run by barclay bank, and have expenses in the
The problem with the TSP, or any 401k type program to my knowledge, is that you can't really buy in at a moment's notice on dips the way you can in a personal trading account. Maybe some have it different... As a result, it is very tough to time things properly when there are business day time lags to make moves.
Now, you are in perhaps an inferior position, as though you have done well being 100% in the international funds, you lack diversification. You may want to re-think this, as buying into the large cap growth companies via the C fund may do well moving forward. Time will tell... But I would merely diversify and adjust your buying pattern/allotments to always buy into the areas that are the best deals (IMO, the C fund right now).
Trying to adjust to keep profits, unless done right at the verge of a major bear market, is a loosing game. There have been many studies done in the short and long term that found that it is extrremely unprofitable to be out of the market on the 5 best days of the year, decade, century, etc., whereas to be out of the market on the 5 worst days had a smaller effect.
Believe it as you wish, there is likely some truth and some ways to have a better strategy... it is on everyone themselves to figure it out for themselves. However, overall, given the relative lack of agility to buy/sell funds in the TSP (regardless of howmany transactions were allowed at any time), you are best off adjusting for growth, and buying into cheap sectors, IMO.
Good luck,
JMH