4Game

I just went to check the battle pass event guide, turns out the "three tokens for a bounty equipment" thing will reset every season, so here's the situation:

• you can get 21 tokens every season
• Lorraine 50t cost 18 tokens
• cobra cost 24 tokens
• if you don't buy 1 extra bounty equipment each season, you miss it

therefore:

• if you don't want to miss any bounty equipment, you buy Lorraine 50t and 1 bounty equipment, using all tokens from season VII, then you get 21 tokens from season VIII, which is not enough for cobra, so you'll need to wait until season IX to get cobra.
• if you want to get both tanks early, you save 3 tokens from season VII, then use all tokens in season VIII to get cobra, missing 2 bounty equipments.

so the best strategy seems to be:

• NOT getting lorraine 50t in season VII (with 18 tokens left), get cobra in season VIII (with 12 tokens left), then get lorraine 50t in season IX (with 12 tokens left turns into 1,200 bonds)

or

• NOT getting lorraine 50t in season VII (with 18 tokens left), get lorraine 50t in season VIII (with 18 tokens left), then get cobra in season IX (with 12 tokens left turns into 1,200 bonds)

Either way, you can't get both tanks early AND not missing extra bounty equipments at the same time. Also getting Lorraine 50t early is a trap.

Edit:
"Trap" is kind of an overstatement, but here's the thing: by choosing to get Lorraine 50t this season you forfeit the option to get cobra earlier, less flexibility. But if cobra turns out to be not worth the hassle, then… nevermind.

for F2P players the situation is a bit more simple

• you get 12 tokens every season
• get 1st bounty equipment in season VII, with 9 tokens left
• get lorraine 50t and 2nd bounty equipment in season VIII, with 0 tokens left
• get 3rd bounty equipment in season IX, with 9 tokens left turns into 900 bonds

or

• get 2nd bounty equipment in season VIII, with 18 tokens left
• get cobra in season IX, with 3 tokens left turns into 300 bonds

it's another "get every bounty equipment or get tank early" situation, the difference is you won't be getting both tanks anyway so less thing to worry about.