I would agree that you can deploy 3 mines, go to the ammo box, grab another 3 mines and place them, too. That is 6 mines total. But when you go to the ammo box and grab mine #7 without even having deployed it, mine #1 will disappear. So the maximum number of mines active in your kit would be 6, not 9. Once a mine is slipping from the storage slot into your hands, I consider it "activated".
Concluision: If you dropped 6 mines and accidentally pick up a 7th mine while passing an ammo box, mine #1 will vanish. Thus I believe in 6 mines but not 5, though I rarely use them.
same thing with s-mines just replace the 3 with 2 in the top sentence.
if you are alive the mines will stay forever (i guess) when you die they will disappear after a short while (i think something like 5 minutes but not sure)
Accordingly to my conclusions above, the maximum number of s-mines active would be 4. Though I'm not really aware. My acting is rather instinctive. Usually I deploy 2 and keep 2 in reserve, if possible.
Kits will disappear after about 20 seconds. Accordingly you got 4 to 5 seconds to regrab it when you spawned. That long mines will definetely stay.
Whenever I had deployed s-mines and died on respawn, the mines still did stay another 16 seconds until next respawn.
After 30 to 33 seconds and the second respawn, the s-mines lose information about themselves but not about the player ID who dropped them. They will stay about another 15 seconds up to a total of 45-50 seconds. This leads to kill messages like "Me[removed with]enemy". The player ID information is still there, but the mine forgot about herself. In case you sit in a static gun or vehicle during the last and 3rd period of existance of that mine, the kill will be assinged to the gun you're sitting in, as the engine is infering to the ID's actual gun to fill the missing information about what killed the enemy.
So after having died 2 times while you deployed 2 mines in the first life, then there are 5 mines active and assigned to your ID of which the first 2 will have forgetten "about themselves". (2x depolyed, 2x undeployed, 1 active and one in reserve).
And that would speak in fact for a maximum of 3 s-mines or 5 anti-tank-mines total.Gotta test this.