hey,
i work in hospitality I've been here for 18 months and i am due to apply for 186 very soon, over the past 18 months 4 of the chefs i have worked with have received there 186, all have left within 3 months with no repercussions. some within weeks and ive heard of a couple previously who just stopped turning up. a few changed industries.
one of the chefs advised me that his agent had told him the terminology on staying is loose "expected" is not have to, it wouldn't be a residency if your still tied to the job just a visa(he used a agent known in his community over the employers agent).
but its best to have a valid excuse the easiest being asking for a pay rise and being refused, or being offered a higher paying job. that way if you are asked you have a response.
this would likely happen if you applied for citizenship.
as far as i am aware there is very little your employer can do with out more cost expenditure to themselves, however this is all workplace gossip and be taken with a pinch of salt.