Debra, just a single-user case, but I finally had an FTDNA sample "retired" after almost 15 years and 16 separate tests performed against it. A Big Y-500 was ordered during the DNA Day sale, and that 2003 sample had finally given up the ghost...er, as it were.
I'm kinda thinking it may be time for companies like FTDNA and YSEQ, that maintain and the store samples provided with tests, to start offering a "warehousing" option: you don't have to pay for a test and crack open a sample vial right now, but can pay a small fee to have the sample(s) stored for future testing. Unopened, epithelial cell (cheek swab) samples should stay viable for a couple of decades, or longer (not so with saliva samples). And it seems a sound business model for the companies: no more than a few dollars cost for a couple of swab kits (that they buy in bulk anyway) with two swabs in each; customer pays shipping; only other costs are handling, receiving, and storage; and it's as close as there is to a guarantee of future purchases against that sample...small profit assured, with no chance of a net loss on the service. Wait; anybody know a trustworthy venture capitalist?
Yesterday I updated the ISOGG entry regarding YSEQ's whole-genome sequencing (https://isogg.org/wiki/YSEQ#Whole_genome_testing) because they've expanded the offering and lowered the base price. They now offer three different coverage (density) options for the tests: 15x, 30x, and 50x. I personally wouldn't bother with the 15x, but the cost of the 30x is now down to $1,300. When Full Genomes introduced a similar resolution test at the end of 2014, it was $1,850; it's come down in price four times in less than four years to also about $1,300. Five years ago, options were limited but you'd have been looking at around $5,000 for that sort of test.
I won't postulate that we're a year away from a $200 whole-genome test, but the cost will continue to drop as HiSeq equipment and techniques continue to evolve. I bet we're under a thousand dollars in a year or so, and under $500 within four or less. With every generation so vital to autosomal DNA's ability to look into the genealogical past, wouldn't it be great if we could pay something like $25 now to get an aging relative's sample in storage for state-of-the-art testing circa 2025?