I installed the untouched apk and it limits you to 10 responses (it doesn't say when it resets). But, I reset it - i.e., I cleared data and cache and the count went back up to ten. This didn't seem to work with the modded version earlier.
The characters are responding now, but it ran out over 6 hours ago. So, if it does restrict you to 10 messages then the reset time is a few hours.