I'm a firm believer in having partials break at a point that invites further reading. When I was querying, I had a five page cliffhanger and a ten page cliff-hanger, because those were the samples sizes most agents wanted in the query. I had a 30 page cliffhanger, but I always felt my 50 page sample ended weakly. I never did get a full request of the 50 page sample, but I did off the others, so I say revise the pages until they end somewhere better.
I did a revision with an agent later that fixed my 50 page sag- and it was a sag- turns out I needed to move up a scene that happened later that was a plot catalyst for things to come.