Carbonation Question?

So I carbonated my beer at 30 psi and it says to give it forty hours of carbonation but I wont be off until later! So could this possibly be a problem such as over carbonation? This is my first batch so I just want to make sure if I leave it a little longer will it be alright!

What temperature?

30 PSI at room temperature should be ok, but if you've got it at serving temp it will be very carbonated.

The guy at my local brew store told me to chill my beer first to 40 degrees and then carbonate at at 30 psi because the yeast that are still active will fall asleep and Co2 is more efficient at this temp so thats what I did!

And I over carbonation a bad thing!

There are a ton of threads on this board about how to properly force carb. With all due respect to "the guy at my local brew store" the method he has suggested basically is you just hoping for the best.

Use a carbonation table to hit the proper volumes of CO2 for the style of beer you are kegging. You should be able to nail it if you have a week to wait using the techniques described in considerable detail elsewhere here on the forum. If you must serve your beer within a few days there is also good advice here on the "shake and roll" method at high pressure for force carbing followed by a reduction in pressure.

Good luck.