A couple of points:
1. It looks like Atomic has a service interval of 2 years and Apeks specifies 1 year (inspection one year, overhaul the next), so I'm not sure that the Apeks will be cheaper for service depending on how much your dealer charges for the inspection.
2. To clarify for others reading, Atomics does not have a "free parts for life" program and I don't think they have ever had one.
3. When I read the stipulations of the "Free Parts For Life" for Apeks, they say that if you miss an inspection or overhaul interval, then the program is no longer available for that regulator. They specify that the service must be documented in the owners manual. For me, that kind of limitation makes the "Free Parts for Life" program pretty much useless.
I do my own service for the family regulators, so I'm out of the loop on how much dealers charge for service kits. I thought they were about $30 each. For the Atomics that would be $120/2 years. If you take how much you would spend on the Apeks and divide it by the $60/year savings on service kits that would tell you how many years it would take diving the Apeks to make back the purchase cost. If the bi-annual inspections for the Apeks aren't free, then subtract those from the parts cost savings.
If you could share your actual costs then we might be able to do the numbers more precisely.
Brian