All investments have a certain lifespan on them - with things like bonds and T-bills, interest payments and maturity are fixed and contractually obligated, while with equities it's up to company performance. To really do well, you have to think like a trader and run all investments over a specific timeframe with predetermined exit signals for profit, loss, or trend changes.

It may look as if Warren Buffett lets money sit in the market. But he is actually running trades over decades of time. He has to - he literally has too much money to make useful(percentage-wise) profit in smaller time frames.