Assuming the target is TCM or fall thon (without reading your entire blog)? Assuming that I'd say 2 tempos a week is too much. Once you get a long run, Tempo, and one other quality day enough is enough.
When training for 5K-10K I'd often run a 5 x 1200 or 5 x 1300 Interval workout as part of a double run day and then follow the next day with a long tempo run. It worked great and gave me more recovery time before the weekend if need be. I think I ran better that season than any other and the only added workout was the long tempo (30+ mins).
I've never even thought about doing 2 tempo runs the same week….interesting though. I think with my workout load that would be too much.