Exit/Entrance
59E59 Theatres, Off-Broadway By Alan J. Miller BOTTOM LINE: This is an intricately structured portrayal of a couple's 40 year life together; definitely worth seeing for the ideas it expresses, for the manner in which it expresses them, and for Linda Thorson's terrific performance. At first blush, Exit/Entrance seems little more than a slim reflection on the vicissitudes of life, its inevitable disappointment…