I remember reading the generic Runner's World and Master the Shift Ryan Hall training plans. They included a lot of things like 800s at the start of the week and a tempo towards the end of the week, plus the long run and other aerobic running. The plan did this every single week. I tried out something like it for a bit and was astonished how terrible I felt trying to do week after week with both types of workouts.
There could be a number of reasons why we find difficulty with this kind of training. My suspicion is that a) we're running them too fast and/or b) we haven't done the fundamental training to be ready for that kind of training and/or c) we need to stop thinking in terms of weeks and expand to mini-cycles of 9 to 14+ days instead of 7.
It's pretty difficult to know if intervals are being done too fast. They're over by the time you can decide if it was too much. Typically, form is a good indicator of whether they're being done correctly. If you're risking a lot of damage to your body by losing form during intervals, then it's not worth it and you should slow down.
You say "tempo" and "threshold" and use them to mean the same thing. Let's go with that, but put the focus on the word threshold. Threshold isn't a pace. It's an effort or a heart rate or ability to process oxygen or whatever, but it's what your body can handle, which is NOT a pace. Theoretically, you should not find much trouble running near threshold, because it's always a pretty safe effort. This means you're probably trying too hard and going over the threshold.
Or that you've just not done the correct preparatory training to handle this sort of thing. Is this your first stint of doing tempos and intervals in the same week? First time at this high of a mileage? Or do you just always suffer through "2 or more hard runs a week more then[sic] 2 weeks in a row" before backing off to recover? If you're "suffering," then I don't think you're even getting the best benefit/adaptation.
My random recommendations:
1) Stop making your workouts, weekly totals, and paces harder than feels comfortable.
2) If you aren't sure you're prepared to run a workout, then you probably aren't. That's a good sign you should alter the workout.
3) Consider changing your workout cycle. Maybe you find two days of easy running between workouts gives you the best recovery. So, do 3 workouts (interval, tempo, long or whatever) over 9 days instead of cramming it into 7. Or make it a 14 day cycle so you can more easily use weekends to your advantage. There's a good argument that VO2max stuff shouldn't happen more than once every 10 days, so that's especially worth thinking about if you plan to keep killing your interval workouts.
4) Don't think that you should be able to handle certain workloads just because you've read/heard/seen other people appear to handle them. Don't make the mistake of thinking it's automatically better to do 30 workouts this season instead of 20. If runner X and runner Y both perform the same on their respective last workout, does it matter whether they did 30 or 20 workouts that season? The point is they're equally prepared to execute the same race. It's not a weakness to do workouts less often if it's what gets you to the correct goal.
5) How is your nutrition/hydration/sleep/etc.? If you were a professional, you would probably be iron tested like ASAP whether or not it was a problem. I'm not saying it is your problem, but simply suggesting the little things are just as important as the running itself.
6) Instead of asking if the tempos have to be done every week, ask yourself across the board what exactly it is that you should be doing during any period of training. Tempo or threshold runs themselves are not inherently bad. It's the timing of them with everything else that makes them good or bad (and this assumes you execute the run properly). You might be blaming the tempo, but odds are that's projecting your training concerns onto something that may be more of a symptom than a cause.