Wow this thread is great for me, as my training mileage and paces, and even race times are almost identical to yours (17:30/37:18/1:22:00). What kind of tempo training are you doing? I'm usually too lazy to do tempo work (I do an interval workout every week and usually one longish run), but if yours looks achievable it might motivate me to start doing something similar. Also, do you notice a big difference with a long run each week? I've found that for everything short of the marathon I'm just as good with high weekly mileage (70-80) spread out over an entire week as I am with a longer run of 15+ miles every week.