lol... How true, how true.
if you haven't done it yet, you can't say you've done it. Period. You have no way of knowing whether or not it'll work out as planned.
Might I also suggest getting an RA position that will last longer than a summer?
Along the same lines as Lizzy's comment, I'd say an RAship limited from the beginning at 1 summer is like asking someone out "until the day before your birthday, then we'll just break up, ok?"
I really have trouble believing you'll get much out of a summer of research when it takes at least that long to even train a new RA much less get a project done. Being a summer RA is practically worthless to the lab and, consequently, you as well. (Esp. since/if the lab is aware you'll be leaving so soon -- why bother training you? Basically, I doubt anyone's going to want to invest much in you.)
This really is, IMHO, one of the major reasons everybody tends to hate premeds.