Only issue being that the estimates one gets from poorly planned sprints are probably less reliable than just asking the devs how long the project will take and going with it.
Good estimates come from watching people deliver over time and scientifically comparing empirical performance to subjective estimates, not asking them to predict. Joel Spolsky has a great blog post on Painless Software Schedules.
There is nothing scientific about this method in my opinion. You do not make consistent reproducible experiments, you do not control for anything, you haven't even formed a null hypothesis etc.
