Changing max bid price of AWS Spot instance
No way ! You cannot change your max price once the instance is running. in order to change the price of your bid, you must cancel it and place another bid.
Can I keep my spot instance in use by modifying my max bid price pro-grammatically(Python boto) as soon as the bid price increases, so as to stop it from terminating itself and manually terminate it once am done with my work. I know I can use the latest spot block to use the spot instance upto 6 hours, but it reduces the profit margin. So I wanted to know if I can modify my bid pricing on the go based on the current demand. 
Thanks.