I've tried this a couple of times. The first time I lost the suction during the middle of the night, but last night, the suction stayed, until i decided to take it off at about 4/5 in the morning. Unfortunately i've got a bad back at the moment and needed to turn onto my side, otherwise i would've left it on all night. The difference this morning is amazing - definate swelling and my husband agrees.
I can also see a big difference on my smaller side (I had implants removed and was left with one side half the size of the other for those that may not know). I can also report that there have been no bad effects on my scars (1 and 1/2 inches long) when using this system, infact they've improved alot, as i've been using vitamin e cream before i put the cups on, which has helped to fade them alot.
I clamped the air by folding the long tube (attatched to the pump) into 3 and tying a hair band around it quite tightly. Unfortunately, i can see this may wear the tube out after awhile, so a proper clamp would be better i think (and less fiddly). I like the look of the top picture - it is the kind of clamp used in hospitals, although i'd probably use two on each side just to ensure the air was locked.
I saw another, more expensive system on ebay the other day that looked exactly like noogleberry, but with a suction machine (so basically you're paying for the suction machine!!). What i did like was that the tubes were attatched in such a way that they pointed downwards, which would be alot neater and would enable you to wear normal clothes over them.
Anyway, happy pumping everyone!