It was actually 6 months...

https://en.wikipedia.org/wiki/111th_United_States_Congress#Party_summary

Look at the 2 blocks where D's had 58 (+2 I's that caucused with them).  Adds up to about 6 months.

But it really counted for more than that, because D's also got to control when any votes were held.  Pretty easy just to hold the votes on the most contentious stuff until you have the votes.

Plus let's not pretend like still having 58 or 59 (especially when both Maine R's were RINOs) along with the House and WH isn't still extremely powerful, and significantly easier to pass your agenda than, for example, the 52 R's have now.