Well, this might not be much of an exploit, however I'm sure it's not meant to work this way.
Achievement is 150 for the Title Master Carver.
In Lion's Arch there are overflows, you can carve each pumpkin once for each overflow. So all you have to do, is stand by a pumpkin and relog over and over again. Carve it as many times as there are overflows, when you've carved it for every overflow. Move on to the next one.
I've gotten about 80 carves this way. Moving forward to 150.
Every day or so new overflows are created and so new pumpkins to carve.