Dear Xavier Sanchez-Korichi,
Before I answer to your question, I have to say you that also if you are enough strong, it’s better if you introduce Depth jumps in the training after the Special Strength Preparation period (see my answer to Sergio Gabba in the thread “Training for the high jump” and to Jason Dwight in the thread “Making things clear about shock training”).
1. I want to do depth jumps with rebounds since I think they are the best but can I do more than that in a session...? Example : Squats and others jumping exercises ?
It’s better if you perform only Depth Jumps in the single training session (see my answers to Marco Pignone in the thread “Effectiveness of Combining Strength or Speed-Strength with Depth Jumps in Same Session”).
2. How much of strength work do I need to maintain my strength ?
I have difficulties to answer this question because all depend on: your specific adaptation capacity, the volume of strength loads that you used before and the type of training program (concentrated or not).
3. How much time (4 5 6 weeks ?) should I do plyometrics ?
If for you plyometric means “Shock Method”, it’s better to start from 2 training sessions per week, performing not more than 4 series of 10 Depth Jumps in each training sessions (the number of series must be increased gradually from 1 to 4). The time of use the Depth Jumps ends when you finish to perform 300 - 350 Depth Jumps .
4. What is the perfect height to begin depths jumps with rebounds
The perfect drop height is 0.75 m. But you must reach this height gradually increasing it starting from 0.45 m (see my last answer to Demetrio Frattarelli in the thread “Making things clear about shock training”).