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.
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.
Changing max bid price of AWS Spot instance