this is how this works. when an employer files a GC for you, based under any employement catagory, it is not a contractual thing that obliges you to be with the employer or the employer to keep you with them. it is just a process, that says, the employer couldnt find any qualified worker ( ofcourse a resident already) so they're willing to sponsor you to be a PR. once you get your PR, you are under no obligation to be with the employer, and neither is the employer to keep you there. the so called "conditional GR" is actually a temporary green card, usually for 2 yrs, the only way thats not gonna be changed into permanent Green card is if you involved yourself in criminal , terrorism, work against the interst of US , and stuff like that. and well, quiet franky, there is no such thing like permanent green card, coz US govt can alwasy revocke ones green card, should they involve in act agains US. as far as changing your employer, that has nothing to do with converting your temporty greencard into a permanet or so called for 19 yrs. good luck.