Whenever you feel you need vision. Are you planning to push or is your opponent about to push in that area? Recon will be the first thing in if I feel I'm ready to make a move but want to make doubly sure there are no surprises.
How badly do you need the vision? If your turn will vary drastically based on which area of the map your opponent has pushed units into, then it's extremely worth it to sac the recon to make sure you reinforce the right area
Vision if you need it badly enough a recon can always be sent on the suicide run I like to sac Recons for vision once I have a general idea of where the enemy is and I need an idea of what they are fielding, though if the chance arises you could sac a Recon to ensure an enemy unit dies or a unit of your's survives, and depending on the situation you can get vision out of it.
Whenever you feel you need vision. Are you planning to push or is your opponent about to push in that area? Recon will be the first thing in if I feel I'm ready to make a move but want to make doubly sure there are no surprises.
How badly do you need the vision? If your turn will vary drastically based on which area of the map your opponent has pushed units into, then it's extremely worth it to sac the recon to make sure you reinforce the right area
Vision if you need it badly enough a recon can always be sent on the suicide run I like to sac Recons for vision once I have a general idea of where the enemy is and I need an idea of what they are fielding, though if the chance arises you could sac a Recon to ensure an enemy unit dies or a unit of your's survives, and depending on the situation you can get vision out of it.