When I worked for a large trucking company - at the time the manufacturer said 10k OCI
We determined, working with the oil company, that OCI could be 100k+ if you swapped filters at 25-30k - we went 75k OCI to be "safe"
For reference - we had deals with that same manufacturer for VERY generous warranty and even if it wasn't warranty - our pricing was such that overhauls were about 1/5 the street price - parts and labor included no matter what dealer did the work or if we did it in our shops. They were ok with it.
Of the 4 years I worked in that department - I can't remember a single instance where we had major component failure due to oil condition. Failures happened mostly due to lack of oil (skipped PM cycles or failure some other way).
Unlikely a manufacturer is telling you to extend OCI so they can sell you another one soon.
