Ok, first-off you're playing WAY higher than I can anymore. I haven't played mid-stakes limit since the days when I lived in LA and could play there and in Vegas. Where I'm at now the only thing offered in the way of limit poker in my casinos
are VERY low stakes, think like $2/4 and $3/6. At these levels I don't pay too much attention to BRM anymore.
But when I did play higher I pretty much followed the standard line of thought about stop-loss and stop-win systems. It's generally felt that stop-loss is a good idea and stop-win is a poor idea. The amounts you set for each of these is up to you and your bankroll.
Expanding on the idea of stop-loss.... It's generally good to leave the table IF you reach a pre-determined loss amount IF you got in that situation by (pick one, or several)... Not playing your best game, Getting fatigued/tired, Losing focus, Plain old being out-played, Getting tilty due to bad beats, Opponents adjusting to your game better than you are adjusting to theirs, etc, etc.
If you got in that situation by plain old bad beats and/or varience though (by this I mean you are generally getting your money in good, but are simply getting sucked-out on the river when the odds
are on your side) , and IF you can handle this without getting tilty or having your play slip (a TALL order sometimes) then you can continue to play provided your bankroll can handle it.
Stop-win systems, on their own, are generally thought-of as a bad idea. Why would you leave a table if nothing has changed and you're beating the game? Having said this, realize that simple things like length of session ARE changes. If you're crushing the game but getting noticeably fatigued/tired/hungry/distracted that this IS a change.
Apart from all this are the psychological considerations. Back when I was playing for amounts that mattered, I would habitually pass-up several slightly favorable situations early in my session. Why? I found that if I started bad, that could sometimes affect my play for the rest of the night. Is such a move +EV? From a strictly theorhetical standpoint, no. Take every advantage you can get, whenever you can get it. From a real-world perspective (for me), yes, it IS +EV, because it keeps me from getting into a poor mindset early in a session.
This may be a similar situation to you and your need to leave each session with a profit. Of course we'd all like to do that, but beyond that, if its going to impact your mindset negatively by winning a lot early and losing it back late EVEN IF YOU MADE CORRECT PLAYS, then, by all means, quit when you're ahead. No shame in that. Mathematically may be the wrong choice if you continue to have an advantage on the table, but from a psychological point of view it may be the best play for you to keep you in the best frame of mind for when you sit back down in the future.
Sorry this is so long and rambling, but deciding when to stop playing has a lot of different factors for different players. So, the cliff's notes version is stop-loss generally good, stop-win (assuming no changes in game/mental state/etc) is generally bad.