Topside Oil change pump - bad idea?

I've recently found out about pumps you can buy to change your oil from the TOP of the engine, through the dipstick tube. I live in an apartment, and I
don't really have anywhere to put my car on jackstands to change the oil otherwise... the pumps cost about $30-$50, depending on features etc.
I browsed around forums here and elsewhere, and found some people who recommended these devices, and others who claimed that topside pumps leave a lot of the sludge in the sump. I thought that if I buy a pump, I could flush the engine every couple of times I change the oil, to try and loosen up as much gunk as possible. Either that, or I could alternate self changes with professional ones, on a 2:1 or 3:1 ratio. The pros could get the built up crap out, but the routine changes I could do myself.
Thoughts? I drive 90 highway miles a day to/from school, plus relatively frequent roadtrips... so I get an oil change about once a month. This could be a significant cost-saver for me...
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I use this type of suction pump to change my oil for an inboard engine on a boat. They work OK, but can be messy storing after you use it the first time.
By the way, you'll still need to get under the vehicle to change the filter.
Bob

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Leave them alone, because they DO leave the sludge in the engine. Get yourself a 16 liter drum and a plastic sump drainer pan: might cost you $15 for the lot. Most garages (esspecially one where you get work done occasionally) will let you dump the oil into their used reservoir.
SD
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