I am a big fan of the strategy of developing using the latest technologies (with the definition of latest being defined locally i.e. it will depend upon various factors, all of which will change from place to place).
Once developed, maintenance should be as minimal as possible. No enforced upgrades of OS, RDBMS, etc.
If a product, upgrading should provide benefits but compatibility should be maintained as much as is reasonable.
-- Stop your grinnin' and drop your linen...they're everywhere!!!