I routinely freeze
dough-like preferments like pate fermentee and biga. (I have not tried this with a more liquid-like preferment like poolish, but that's mostly b/c I don't have the freezer space).
I may double or even triple my favorite preferment recipe so that I have a good supply in the freezer.
Tips for Freezing Preferment
A digital kitchen scale ($25-35 USD) is recommended.
Make your preferment recipe, increasing the quantity if desired. If you let it rise at room temperature, then stir or punch it down and chill it in the refrigerator until it is completely cold (it will continue to rise some in the 'frig during this chilling stage). When cold, weigh out portions in a convenient amount (I generally make 8oz portions). Double-wrap each portion in plastic wrap and label each package with the amount, date, and preferment type.
If you don't chill the preferment before packaging it for freezing, it may
continue to rise a bit in the freezer, since it takes time for cold to penetrate the interior of the preferment. This depends on the size and shape of your packages and well as the temp of the freezer. I like to shape each package as a flatish rectangle so that it will freeze quickly.
As you know, you can hold a preferment in the 'frig for up to 3 days before using it in your bread recipe. However, when making a batch of preferment explicitly for freezing, I prefer not to hold it for any more time than necessary in the frig. This is because the preferment does continue to ferment very slowly in the 'frig. If you're manipluating the rising time of the preferment itself to get a more pronounced flavor you can do this when you defrost your preferment packages.
Tips for Defrosting Preferment
I prefer to defrost the preferment in the 'frig rather than at room temperature. If you defrost at room temp, the yeast activity may resume on the outside of the package while the inside is still thawing. This depends, of course, on the weight and shape of the frozen package, as well as the ambient temp of your kitchen.
I usually put as many packages of frozen preferment that I will need in my final recipe in the 'frig to defrost the night before I plan to make bread. You can, of course, leave these packages in the 'frig longer (up to about 3 days), especially if you're looking for a more pronounced yeast flavor in the preferment.
If the preferment was a relatively firm dough, just let it thaw still wrapped. If it is a wetter preferment such as the one posted in http://discusscooking.com/forums/showthread.php?t=14495
then you should check the beginning of that thread for defrosting tips.
If you do defrost at room temp, I find it takes about 1-1/2 hours for an 8oz package to defrost.
I do not think it is necessary to bring the defrosted preferment to room temp before adding it to the final dough. Adding chilled preferment will, of course, slightly slow down the final rise(s) but not to any appreciable amount.
Storage Length for Frozen Preferment
The longest I have held frozen preferment is about 3 months. I do not
experience any degradation of the rising power of the preferment. My guesstimate of a max storage time would be 6 months.