Slow down blind SQL injection

Hello all

Today I was barainstorming and came up with an idea that my help slow
down blind sql injection on a web application.

I remembered that usually a user will read a page before subbmiting a
new query, and that takes time, so why not keep a timestamp on the user
session and enforce some time between queries?

I did not search to find out if some applications out there are using
this, but I would like your input on the folowig:

1. depending on the timestamp, do you think the users will be very
anoyed at some error asking them to try again in a few seconds?

2. given that most automated SQL injectors deped on a boolean result
form the query, and this ends up serving a thrid page, how much will
this confuse those tools?

3. Assuming that the pogrammer will log several attempts, will this
help to find and correct blind injection points?

Thank you all