How would you negotiate this regarding air-conditioners

[Steve S.]

I have a house under contract. Pretty turn key. 20 years old. Seller asked $360k. I got it for $350k

Has two a/c units with heat pumps. Both are original equipment. 

Inspection says they wouldn't repair them. They may keep working ok or maybe I have to replace immediately. 

Probably $12,000 to replace both. I countered with seller paying all closing and prepay - about $7,000 and reducing price $5,000. 

They re-countered with paying $5,000 and suggested they didn't haggle in my original offer

What would your next move be?

1) would you put the a/c under warranty and hope and pray and when they eventually fail use the warranty?

2) re-counter to the seller?

3) accept their offer?

3) other?