to change cast iron pipes or not

I recently purchased my grandparents home, built in the 40's. We are starting the upstairs bathroom remodel. The question is, do I replace the cast iron pipe for the toilet? It looks to be in good shape and does not leak. The outside (all that I can see) is not cracked and the inside is not flaking badly. I hate to redo the bathroom and then have something go wrong with the old pipes. But, if theres nothing with it I really don't want to replace it if I don't have to.

Leave it alone. Make sure the flange is in good condition, and replace it if it is broken or rusted. Removing cast iron is a very difficult job as cast iron is very heavy and it takes special tools to cut it. I did it in my home years back, and found out the hard way how much work it was, but it was too late to quit, had to finish.

Thanks Gary! I appreciate the advise.