Bulk purchase of iTunes Gift Card. How and what?

Question

Apple App Store

Hello colleagues!
We decided to give iTunes / App Store Gift Card in our service. I came across a lot of stores online that sell them, but given that we need quite a few of these cards, we would not like to buy them from intermediaries or resellers. Maybe someone knows where these same shops take the cards?
Also interested in the question of expiration date. I heard that cards become useless after 3 months. This is true?

Answer 1

I bought on plati [dot] ru.
I found a seller with the lowest prices and bought.
Or www.apple.com/itunes/corporatesales
store.apple.com/ie/browse/home/campaigns/corporate...