This a very old question, but a very interesting one. So here is the answer.

The theory says that there as many longer streak from steak X as there are X streaks.

For example theoretically we expect this kind of results:

100 single streaks B or R

50 double streaks BB or RR

25 3-streaks BBB or RRR

12 4-streaks BBBB or RRRR

6 5-streaks BBBBB or RRRRR

3 6-streaks BBBBBB or RRRRRR

plus 3 more streaks longer than 6 in a row.

You get the idea.