I haven't had issues doing a SDC on multi-segment itineraries when the subsequent segments are outside 24 hours. It wouldn't make sense to SDC ORD-SEA to a later time when that departure is after the subsequent segment SEA-GEG. Once the SDC is processed, you won't be able to check-in for the later itinerary until 24 hours before departure. If it is an earlier flight, you can continue with check-in.

Similarly, when you check-in, you are checking in for all segments on that date and will get boarding passes even for flights that aren't available for OLCI if they were O/D only as they are still outside 24 hours.

When I checked in Thursday for PHX-SEA-SFO-JFK at T-24 for the first segment I got boarding passes for all three segments even though the departure for the subsequent flights were well outside of 24 hours. On Friday, I checked-in once for the Saturday segments.

OLCI can only handle 4 segments so if you have 5 or more segments on the same calendar day, you will need to see an agent at the airport to check-in and get boarding passes. A kiosk will not work either.

James