Raising two puppies question

[Groenendael]

Question to people who have raised two (or more) puppies at the same time!

I know that most people are against having two pups at the same time. But the puppies are here, and I hope I will be able to do this.

A bit of background; The puppies are siblings, 4 months, a male and a female (Belgian shepherds). I am not going to work for at least a year. I have got the separation-part all sorted out; crates, training, walks, feeding. I am competing agility at the highest level (right now with my 6 year old dog). My life is basically dedicated to dogs, their well being, and training. Also, I have a "way out" if this wouldn't work-out; the breeder will take one of the puppies back, if I feel it starts to "get out of hand".

To my question, and this might sound silly, anyway: How often did you let your puppies play together, once a week, once a day? What would be the aproriate time to leave them to play (10 min. 30 min.)? I actually keep them separated all the time at the moment.

Thank you so much for reading this, and I am looking forward to hearing your answers!