"I would have seen a return of approximately $7,500.00 in distributions. Could I expect similiar returns in coming years?"
Tinker,
Not necessarily.
If you don't understand how bonds/bond funds work, at the very least you ought to go to the Morningstar School and read about them. You can find the tutorial by clicking on Personal Finance at the top of this page. When that window comes up, on the left side of the screen in the Personal Finance Box, you will see Bonds and Bond Funds. Click on that and read.
The short answer to your question is that when interest rates are cut those cuts will eventually manifest themselves in your bond funds (in their distributions) when the underlying holdings of those funds are issues with the lower rates. Conversely, when rates go up eventually so also will your distributions.
If you want to see history in action go to the Vanguard website and bring up the Total Bond Market fund by clicking on Research Funds and Stocks. When you have the Total Bond Fund in front of you click on Performance, scroll down and click on See Cumulative, Yearly, Quarterly Returns. In that window you will see the Income Return in percentages going back to 1993.
A rule of thumb with a bond fund such as the Total Bond Market Index is that if you hold that fund for as long as the average duration of the fund's underlying holdings - in this case about 4 1/2 years - your Income Return will be the average of the Income Returns listed for that period. So, take any five year average of the Income Percentages shown and that will give you an idea of the distributions for the Total Bond Market Index fund for whatever period you choose. Then, see what the interest rate climate was for those years.
Beginning in 2000 rates were relatively high. Then the Fed cut rates for several years running. By 2007 they were raised again. And most recently you've seen them cut.
One thing is certain. Just as no one can predict how the stock market will perform neither can one predict what interest rates are going to be.
Hope this helps.
Billym