I'm afraid I take the opposing view - it's very much their business if I'm planning to leave, and I shall be giving my employer as much warning as possible if I have my place confirmed, rather than just handing in my resignation precisely one month before I leave, because I don't want to leave them in the lurch! However, it would NOT be the same situation if I was seeking another job in the same field, but because I m contemplating a career change, it makes it much easier to be open with them - in the end, we'll all benefit from that, whatever happens.