Archie,
IMO, most important thing to remember is you do have options.
It doesn't have to cost $2M+
We are working on a course right now where we are utilizing most of the pipe, because the club is not reporting pipe failures.
That is unusual, but the system was professionally designed 20 years ago and they could perform simple mathematical calculations 20 years ago just as well as we can today, and PVC hasn't changed much in 20 years and they specified the proper pipe.
One thing to look very close at is sprinkler spacing. You'll hear numbers like 60' as if it is the auto default, some magic number. But the reality is while you may get an 89% distribution uniformity at that spacing (in a windless lab type environment) you can get 86% or so at 70-75'. If you use 20% larger spacing, you don't save 20% of the heads because heads irrigate a circle (ignoring PC along edges for a moment), it takes 56% more heads to cover a given area with 60' spacing vs 75' spacing. And with single head control where every head can be its own zone, and with topo changes, soil moisture measuring devices to help schedule, simple tools like your phone, ipad, or radio to spot water, is it really worth 56% more heads at about $1300 each to pick up 3% in DU?
I think staying on top of your cultural practices like controlling thatch and managing compaction so you maintain some infiltration is way, way more important than having heads 10 feet closer together.