I'm going the same route for a barley wine to be brewed this weekend. I was going to try and prime the keg, but have concerns about the yeast being up for the task with my high ABV. I plan to basically hit the keg with 30 psi to seat the lid, and then leave it hooked up to the tank for a week or so with the proper psi to get 1-1.5 volumes of CO2 into solution. This way the lid should stay nice and tight during cellaring. My concern with hitting it with 30 psi and then forgetting it is that eventually the beer will absorb the CO2, pressure will drop, and my seal might be lost. Next year when it becomes time to drink, I'll chill it and put it on pressure to get the carbonation I desire.