I agree with Faz. You shouldn't be overtraining as you will be using sub-max loads for all but one of your w/os every two weeks. It is only once you have entered the post-5s that things get a little more brutal.
Ordinarily, I wouldn't drop any loads for work sets. However, sometimes during post-5s, when I'm pushing for new RMs, I might do this sort of thing:
Warm-ups then:
1st set, 5 x New RM,
2nd set, 5 x Previous RM,
3rd set, 5 x Previous RM
Assuming I get the new RM, I might do this the next w/o:
1st set, 5 x New RM,
2nd set, 5 x New RM,
3rd set, 5 x Previous RM
If that went OK I could then do:
1st set, 5 x New RM,
2nd set, 5 x New RM,
3rd set, 5 x New RM
So I'm not using the same load for all my worksets until I've worked up to 3 sets with my new RM. Then I might start the process again if my body was still coping OK.