Buy for 3yr old VEX IQ kits (classroom)?

Background: I have 9 VEX IQ kits we’ve used for 3 years with around 90 5th graders each year & a very small budget.

If/when I get extra money, should I buy items my kits didn’t come with (Smart Radios, gyro & distance sensors) or should I buy backup brains in case they start to fail?

I know there is no magic answer, but I would appreciate advice from more experienced users.

I think this would really depends on your program. Are you getting new kids each year, so you don’t have time to get to the more complicated parts like gyros and sensors?
I will say that the smart radios have been a bust for us so far. They are limited by what they connect to, and which programs you can use.
Good luck!

Batteries and connector pins! The competition kits are cool too. I also agree with everything above.