I like the NO RANDOM DRAGONS model myself. With my second character / play through I avoided the main quest until Balgruf insisted I had to attend to the Dragon Issue at the Watchtower during the Civil War questline. So turned in dragonstone, went to Watchtower and did the quest. Figuring, well at least I can activate some shouts now, visited greybeards also. While finishing up the civil war quests (Imperial), I had two random attacks, both occuring when I arrived at a Legionaire camp. Afterwards not a single random spawn. I think this is because I stopped the main quest prior to visiting Kyesgrovew/ Delphine. This is where one learns tha Alduin is resurrecting his kin.
Anyway, its nice to discover dragons at their lairs / word walls, while traveling, you usually see them soaring around, but even better not to have them dropped on you the moment you pop out of a dungeon or a fast travel. You won't gain enough souls to activate every word, but enough to get a nice selection of the best ones.
I've used this game approach on 3 characters now with consistant results, no random dragon spawns once the the civil war is concluded. But dragons and their souls are available still to cash in on some of those words you learn....