Unfortunately their is no % or rule of thumb in terms of what you're asking, it is such a broad scope esp now with the leed compliance's, reclamation, co gen, re heats, staging, lead - lag as well as the the other comment regarding efficiency, type, environment.
The rule of thumb is that their is no rule of thumb and even for feasibility estimates. I still perform a level of breakdown unless it is of no importance at all.
Regarding the the life cycle, everything manufactured has an mtdf (mean time before failure) this is relative again, to environment, presumed level of maintenance, use, how it is managed, and finally the original design in terms of under / over sized criterion. (for replacement value) This is "presumed" the existing technology isn't antiquated by the end of its life or even abandoned all together.