I worked as a drain cleaning plumbing tech so I am only familiar with sewage pipes.
We only saw the worst case scenarios, mostly old clay pipe with tarred rope at the joints, but some pvc pipe.
The pvc was alway broken right where it entered the house.
This probably had everything to do with frost heave in a zone 6b climate, and poor installation.
All that said, pvc pipes 18" deep in a warm climate should be extremely robust and unlikely to leak.
Repairs, if needed should be pretty easy, but of
course, no one wants to create problems for themselves.