Telcel information

I can't seem to find two pieces of information: How long are the pesos on a phone good for? Went to the Telcel guy, and he didn't know. It's something like 20p is good for 2 weeks, 100p 2 months, or something like that. Yes, this is assuming the phone is not used. Help, please.
Second question: What is the emergency number for Mexico highways? Thanks