What spans can 6X12 beams cover?

I have a similar topic in another forum, but thought a different angle question would be better here:

What kind of spans can a 6X12 beam cover?

I have an opportunity to get a 100 or so fir 6X12s that are 23 feet long for $40 each. They came out of an old shopping mall being torn down. Don't know if that's a good deal or not, but this question is more to the application? For that length, are they way oversized???

Thanks....

There are so many variables to this question that it can not really be specifically answered without more information. How do you plan to use the beams? A residential floor live load is required to be 40 psf (plus dead load). If your use is for roof framing, snow loads may range from 20 psf to 300 psf around here depending on the elevation above sea level. What spacing will you be putting the beams? The tributary area of each supporting beam is drastically affected by spacing and span. The 23' long beams you described could be put to many uses - if it's a good buy, you probably should go get them!