I've got the B&Q 850w SDS. Done loads of heavy chiselling with it and it's still alive. Great tool.
I'll tell you about the grease. I've been pretty meticulous about topping up. It only seems to get used with hammer action turned on, but in that mode mine runs dry very quickly - say an hour or so's continuous use.
At first it seems to be going nowhere and its fate is a bit of a puzzle.
Then you notice that you no longer need to grease the base of the SDS bits. The grease is working through and lubricates them automatically. Neat feature, you may think when you first notice.
Then you find the odd greasy splodge around the nose of the drill, and on your work. Hmmm.... not so keen on that, but not a major problem for the purpose of wanton destruction, which is what I bought it for.
Later still, it appears en masse in the ventilation slots around the motor housing. Yuck, and you can't clear it easily.
Then it starts to work its way out and you end up with greasy smears on the casing of the drill and even bigger splodges being blown out at random. Get too close during the difficult bits and you acquire a big greasy patch on your clothes.
Finally (several days near constant action) the drill degenerates into a disgusting greasy morass that you don't want to touch even with gloves and overalls on. Mine is currently exiled to a piece of cardboard on the garage floor while I pluck up the courage to pull it apart for a massive clean-out.
Apart from that it's fine.
W.