Backing up another half mile from Page Road (that is, about one mile from the I-540 exit) we have the Miami Boulevard exit. There must be some way to get an I-540 advance notice on this signage: https://goo.gl/maps/fkw3qgGWi2kUYraE8.
The bigger problem here is that the Durham Freeway has a left-hand onramp prior to Miami Boulevard. Now that you've pointed out the lack of advance signs for I-540. I'm wondering if NCDOT has intentionally omitted the advance signage to discourage movements from the Durham Freeway to the northern leg of I-540 (now it's simply I-540, as the southern leg has long been reposted as NC-540). It is typical in North Carolina to give a lot of advance notification of an upcoming major interchange, at least 2 miles for arterials and usually 5 miles for freeways. One of the main issues is when too much traffic crosses from the far left lanes to the far right lanes too soon (or vice versa, like the move on the Capital Beltway from the Cabin John to I-270), all of the traffic flow models predict the need for a flyover. And that is not always the best solution.
I've never seen any 5 mile advance notice of an upcoming interchange in NC. But the one I always think of when Eastbound I-85/I-40 split apart approaching the Triangle. There's something grandiose about that interchange because over the years I had several people from Atlanta call me up saying they thought of me while passing the Raleigh exit off I-85..
I hope the diagramatic arrows were removed when the European style split signs became the norm a few years back.
For the most part, interchanges are not signed in ahead of the previous interchange. The first sign is typically on the same sign structure as the exit sign for the previous interchange. For instance, the sign on I-40 east is on the same structure as the exit sign for Page Road. I asked about providing more advanced warning, and the answer was that they thought that signing for an interchange ahead of a previous interchange would be confusing. (Say, signing for I-540 at Miami Blvd might convince some drivers that they need to exit at Page Road. That's the thought process; I don't necessarily agree with that in all locations. But I'm not in Signing.) It has nothing to do with the Durham Freeway on-ramp. There's sufficient room to weave over from the left to the right in those ~2.5 miles.
The I-40/85 EB split in Hillsborough works better because there's a couple of miles between the previous interchange and that split. Not so for the I-40/I-85Bus. interchange in Greensboro (the older split. The newer split isn't signed in advance of the previous interchange either, IIRC.)
Virginia does sign some splits in advance of previous interchanges; one I'm familiar with is the I-95/I-295 split north of Richmond. A sign informing drivers of that split is ~5 miles ahead and at least one interchange in advance. I don't recall a similar sign in NC, although there's some information on the multiple exit signs in the median on, say, US 64 or I-440.
What I didn't care for is when they changed the lane configuration of the split a few years ago, they didn't provide a lot of advance warning that the left lane was now an exit-only lane. Had to make a last second maneuver. (Making a lane continuity change after ~40 years needs some signage/warning. Some of us are set in our ways!.)