Android beta APK distribution problem

I'm going to a Hacker News party in DC tomorrow. I'll show my android app. I want to have a QR code for people to scan and try my app

Should I pay attention to sending unpublished APK to strangers? I heard that suppliers upload their beta APK to other people's accounts. I plan to finally put it on the Android Market for $1. I uploaded an initial version to the market to save the package name, but what prevents someone from re signing with their information? Is this even possible?

I want to sign with a key that expires in a month to prevent people from running the beta forever. Is this useful?

resolvent:

Well, you seem to have several options

1) Upload your application to the market and sign it with your long-term key. In this way, users who install the application in the conference will be able to receive updates. The only disadvantage is that you must publish it as a paid application. Once it is published as a free application, you can't change it!

2) Sign the application with a key that is about to expire. Start with Android documentation "If you plan to support the upgrade of a single application, you should ensure that the validity period of your key exceeds the expected service life of the application. It is recommended that the validity period is 25 years or more. When the validity period of your key expires, users will no longer be able to seamlessly upgrade to the new version of your application "It seems that users can still run your application, but cannot upgrade when the key expires

3) Let your application enforce the "beta" by checking the system time. If it exceeds a certain point, access to your application is not allowed