How long do I have to apply for my wife's petition if she entered the US on a B1B2 visa?

In theory there is no limit. In practice I would apply as soon as possible because as a B-2 overstay she may be picked up by ICE at any time and deported and then the procedure will be more complicated and more expensive. If we can assist you in the process contact me as indicated below and I will provide instructions on the procedures, forms, documents, and fees required and provide medical instructions.

There is no time limit for when you have to file an petition for your wife. However, once her B1/B2 stays expires she beginning accruing unlawful presence. If she accrues 180 days or more and she departs the US she will be barred from returning for 3 years. If she departs after 1 year the bar becomes 10 years. If you are not a U.S. Citizen then your wife should depart before triggering any of these bars. If you are a U.S. Citizen you should still file the petition and her adjustment of status before the 180th day to avoid triggering the bar should she have to leave.