You know, those trial periods using the different internet sources are actually quite helpful. My current subscription to Ancestry.com started that way. I started it with the idea that I might be able to search out all I needed during the two week trial. A foolhardy idea, I know. Even though I spent almost every waking moment working at the searches, I quickly realized that even if I did find everything I searched for, each search inevitably ended in needing a new search.
This week I put the free 7 day trial at Footnote to good use. The Civil War Confederate records and the World War II Army Air Force records were of specific interest to me, having quite a few ancestors from North Carolina who fought for the Confederacy and a distant cousin who died in an airplane crash during World War II. After finding quite a few Civil War records, and even a few Revolutionary War records, last night, right before the trial was to end, I found a record of the Army Report submitted after our cousins aircraft was shot down. There were twenty-four pages of information, the first page of which confirmed that this was indeed our cousin. It was an exciting find, and certainly worth the efforts expended during the trial. However, after this find, I reviewed their currently holdings, and found little else that might be of use, so I let the trial lapse.
I also tried the 7 day trial at Genealogy Archives, but had very little luck there. I entered quite a few of our family names in the general search, and came up with only a few results, all of which I had already found at Ancestry.com. In my case, I didn't think it would be very useful, and let it lapse as well.
So if you're considering trying them, I'd say do it - especially if there's a free trial period.