While I agree with what Lusche said the answer isn't really that simple.
You have enough perks to buy approximately 12,500 Shermans or 2,000 Tigers. Based on your average number of vehicle sorties over the past three months, that means you have enough to drive Shermans only for the next 21.5 months or Tigers only for the next 3.5 months, assuming you lose every one.
So, the real questions are How old are you (i.e. are you planning to die soon)?, Do you plan to drop your subscription at some point? or Are you simply saving for your retirement?
The answers to these questions will guide your decision.