Absolutely time is a consideration for some people. But which direction? Some folks (me for one) like DIY stuff, and feel I get a good chance to check out other things like ball joints, grease zerks, etc when under the truck. But - some people don't like that, are not good at it, or simply don't have enough time for it. The ROI most certainly can take into account "down time" as a cost, but only if it truly affects income. Otherwise, it's just a hobby.
For condemnation levels, check out this link:
http://www.calrecycle.ca.gov/Publications/UsedOil/2008020.pdf
Page 11 has the condemnation levels from major OEMs. Note that Isuzu/GM ins't on there, but it's reaonable to see some common ground where perhaps 75-100ppm would be safe. As I said, 50ppm would be ultra safe, and proably more conservative than necessary. The whole article is a good read, but I find the condemnation levels of special note. Most people freak out when they see a high ppm count, but it needs to be taken into context. 50ppm of Fe in 50k miles is a great wear rate. 50ppm of Fe in 10k miles is high wear rate. Neither is dangerous, but high wear rates can indicate problems and caution is needed. The thing to understand is that BOTH wear rates, and wear totals, must be understood and tracked to really have a good feel for how the equipment is progressing in it's lifecycle.
As for the UOA cycle, that too is something that must be experimented with to find a good ROI. My earlier point with Amsoil's 3x factor is that they don't require a UOA up to 3x the OCI to honor the warranty, and so the UOA cost can be avoided. So, in theory, if the OLM was telling you that 10k miles was a reasonable OCI, and you could go 3x further on Amsoil, then 30k miles is close to your ROI. However, if you use a premium expensive filter, that will push it out a bit further. Since AME is easily 3x more money than dino, then the OCI needs to be 3x to break even (plus filter cost above what a "normal" filter would cost). Given the performance I see in this UOA, I'd say that's attainable.
However, longer OCIs with no UOA takes away other benefits gleaned from UOAs, such as contamination knowledge (dirt, fuel, coolant intrusion).
It's a catch 22; it's just darn hard to justify UOAs in small sump systems.
For example, I can run dino HDEO for $2/qrt, and change oil every 10k miles in a Dmax, and still have money to UOA from a lesser expensive service, and KNOW WITH CERTAINTY all is fine, whereas the Amsoil 3x approach only PRESUMES all is fine.
It's a bit of a game; some are good at it, some are not.
This UOA simply shows excellent wear in the engine and excellent lifecycle in the oil. It's a good start towards earning the ROI.