I've written a response to this post a few times and after I get done typing it just never looks right. Explaining stuff is sometimes not my strong suit. So, I will just tell you what I would do in your situation. If anyone wants to elaborate on it they should feel free LOL.

Build three racks using Petmate Value Line litter pans. Make these racks 10 levels high. Using 2x2s and only leaving 2" between levels (with casters) the ten level high rack will be 72" to the top of the top tub. This is perfect. Obviously, the watering system will add additional height, but that's fine.

Two of the racks will be used for breeding. You should run 1.4 mice per tub, for a total of 40 females per rack.

One of the racks will be for growing out breeders. In the growout racks you should use the top two tubs to house males, 5 per tub. Then use the bottom 8 tubs for females, 5 per tub.

Follow this rotation closely.

Rack A = breeding rack
Rack B = breeding rack
Rack C = grow out rack

At the start of this little adventure you will want to fill Rack A with 12 week old mice and let them have at it.

In the first litters you want to hold back 10.40 mice and put them in your grow out rack.

Once they reach 16 weeks old you move them into Rack B and allow them to start breeding.

Now you fill Rack C with another 10.40 replacement animals. Once these animals are 16 weeks old you use them to replace the mice in Rack A, which are now approximately 1 year old.

Under this rotation you will be replacing 12 month old animals with four month old animals on a continuous basis.

You will also need some holding racks as well, to store the weaners that you are not holding back for breeding purposes.

If you follow this plan you should be just fine. Keep in mind, my expertise is in rats...not mice, but they are very similar in terms of their production.