Buying poop for the first time

Hi guys, I'm buying a girls poop for the first time and wanted some advice.

If anyone with experience could give me some guidelines and potentially mistakes to avoid that would be great.

My main concern is, how long will the poop last in a plastic container before it degrades?

I mostly want to smell and smear, while eating very small portions over a long period of time, since I am so new to this.

Thanks in advance!