Are long-living transactions acceptable?

Question

I am thinking about using transactions in 2-tier WPF (or windows forms) applications in following way:

We can begin new transaction when we open new form for editing

Answer 1

I agree with Mitch n Cheeso, but still there is one more way of putting Timeout on the window, you can notify a clock that if user does not press "OK" then the window will be closed automatically and everything will be cancelled.

Majority of systems where transactions are critical like "Reservation" process on airline, movies etc, operators are supposed to close the transactions in limited time.