一年！

<sessionstate timeout="525600" />

会话超时的最大限制为525,600分钟，即365天x 24小时x 60分钟.

去那里 [会话超时的最大限制] [

The maximum limit for session timeout is 525,600 minutes -- i.e., 365 days x 24 hours x 60 min.

go there[Maximum Limit of Session Timeout][^] to read whole article

保持ASP.NET Session Alive Ad Infinitum [ ^ ]