Hi, you may be pleased to know that 60-odd clients isn't really that big for a CUA implementation :-)
General rule of thumb is that you always split prod & non-prod. Prod CUA master should be on the system with the greatest likelyhood of availability & the same rule to the non-prod systems. Having a regularly refreshed test box as a CUA master is going to cause a few issues....
You need to think about how you are going to be using the child systems. Assuming that prod is separated (different team performing admin perhaps) then will you have one set of admins for Dev and another for the rest? We can achieve segregation through S_USER_SAS so that segregation doesn't have to be performed by having different masters.
Based on what you have said I would be thinking generally around 1 CUA for Prod, 1 CUA for Dev & Test, 1 CUA for Training & Pre-prod. You could have a separate CUA for each tier if you really want but may be overkill unless it is mandated by company architectural or regulatory requirements.
As Mr Voros commented, also consider this as an opportunity to use IdM.