"How much runway" is completely above-the-board. If they won't tell you, run. "What's the end-game?" will probably give you the runaround -- it certainly has

"How much runway" is completely above-the-board. If they won't tell you, run. "What's the end-game?" will probably give you the runaround -- it certainly has for me, with silly redirects like "we are more interested in building value for our customers" when it's obvious that management is always extremely concerned about the long-term plan, so this is interesting to write down and compare to what happens later to see what they say, but of no real use during your interview process.