It is not certified for it so be careful.
Wake vortices decay as a function of time, not distance. Approach controllers convert time into distance as that is what they work with. I would suggest that most TCAS equipped aircraft have a greater TAS in the en-route phase than established on an ILS approach under radar vectoring.
Being 5 miles ahead on the same route can be a threat in en-route.
If you are climbing and falling in behind another aircraft in this situation, you have a high probability of an encounter if the othe aircraft is level and you then climb up through its descending vortex.
Yes, it is a real threat and I have worked on a couple of accidents related to it. However, as there were no regulations that the controllers had broken in these countries and the national investigators were part of the government (as were ATC) then it was never pressed home in the reports. Oh, in both cases the pilots were blamed but they all died and nobody stood up for them with the technical knowledge to prove otherwise.