the perriniana will likely take at least 15-20 years or more to get 30' (at least that's its performance here)---especially if you are not giving any extra water or fertilizer after establishment. all eucs will be better behaved and hardier if they are NOT planted in a lawn (which gets extra water and fertilizer) and left to survive on natural rainfall. all the hardy eucs are potential medium to large trees sooner rather than later under oregon conditions (which are often much better than their natural habitat). as said before, almost all eucs respond very well to hard pruning back with vigorus regrowth as they are natually adapted to surviving storms, fires, and frost in just this way. a healthy euc will take periodic (every 3 years or so) cutting back indefinitely as long as it is done correctly (in late winter or early spring) and will look very nice if you will selectively remove most of the resulting sprouts to concentrate on just one or a couple of well placed stems to become the "new" tree stem or stems (just like pruning rosses).