Working up to a heavy double on speed day

How often should you work up to a heavy double on the bench and box squat, after your speed work? I heard once a month or so. Is there a certain percent that your speed work should be at for this work out (i.e not the last week of a 50, 55, 60% cycle)
Thanks
Will42

I try to do it at least once every 3-4 weeks. But I dont think that it can always be planned. Only do it when you feel good. Some days I can go through my box squats and I feel great, other times I can barely make it through the session, let alone work up heavy. Also remember that if you work up heavy on this day, you must take that into consideration on your next Max effort day. That is, depending on how heavy you go.

Very good advice …