True enough. But going from an arbitrary point within the UFP to beyond the farthest limit of exploration has never taken years - in "Tin Man", it's a matter of only "several days", or 28 stardates at most. The bulk of the travel time in "Q Who?" could thus still be assumed to be between J-25 and the general starting point within UFP territory, as it would make limited sense for SB 185 to lie much farther out than Beta Stromgren did in "Tin Man".
At best, we would be looking at a situation where the bulk of the 8,000 ly Federation lies between the starting point and SB 185 / J-25. But even then, the bulk of the Federation has never been that big an obstacle, as this thread stands testimony - so we're back to square one or thereabouts, and quite tempted to assume that the starting point and SB 185 or indeed any SB will be much closer to each other than those thousands of lightyears.
Sure, I'm not debating how long it would take to cross Federation space - only that we lack distance information for the J-25 example.