Are you talking about the 800 minute national plan? With that plan, you won't ever get charged long distance. You can be anywhere and call anywhere in the U.S., it would just use your minutes. If you have the local n/w minute package that starts after 7, you wouldn't have to watch your minutes, because it would be unlimited but you would have to be in the local area in order to utilize the n/w. However, from the local area with the n/w, you have nationwide long distance. Hope that helps.

If you are calling from within your local call region, nationwide long distance is included, even if you are using nights and weekend minutes.
If you are not in your local call region, such as in California, you'd pay no extra charge in you are on the national plan. If you are on a local plan, you'd just pay the flat per minute roaming charge. I assume you meant you were calling Michigan after 7 from within your local call region, using nights and weekend minutes; no long distance charges for that.